#precalculus

1 messages · Page 309 of 1

viscid thistle
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Guys I'm confused on how u would use l hospitals rule to evaluate the limit

mental steeple
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Can anyone help me with this I’m not sure what to do next

tight compass
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Trying to show what you have is equal to something?

mental steeple
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Simplifying the tanx+cotx /csc^2

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@tight compass

tight compass
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simply to what?

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Hmm try to get sin^2x + cos^2x in there.

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@mental steeple

mental steeple
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Just simplify

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Simplifying simple trig expressions

tight compass
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You need end up with something nice.

mental steeple
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okay

mental steeple
tight compass
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Observe you have sinx/cosx + cosx/sinx.

mental steeple
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Yes

tight compass
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What should you do to get sin^2x + cos^2x?

mental steeple
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Multiply?

tight compass
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Yes.

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Try to get a common denominator cos(x)sin(x).

mental steeple
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Do I do

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Sin^2x + cos^2x / sinxcosx

tight compass
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Yes.

mental steeple
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And divide all that by 1/sin^2x

tight compass
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Yes. Also what does sin^2x + cos^2x equal to?

mental steeple
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2sin^2xcos^2x

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Nvm I’m not sure

tight compass
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Huh? That is not right.

mental steeple
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how would I add that

tight compass
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Try to recall pythagorean theorem.

mental steeple
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Oh it equals

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1

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😂

tight compass
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Yes.

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After that you should get something simple.

mental steeple
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Then divide?

tight compass
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Yep.

mental steeple
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This is what I got

tight compass
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So what are you left with?

mental steeple
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sin x cosx

tight compass
#

Not quite.

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Try again.

mental steeple
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Did I divide wrong

tight compass
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Yes sort of.

mental steeple
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what did I do wrong

tight compass
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You have sin^2x/(cosxsinx).

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What do you think should happen?

mental steeple
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Where do I have that

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Oh did u cancel the 1s out

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?

tight compass
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1 * a = a.

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a/1 = a.

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Do you know how to multiply fractions.

mental steeple
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Idk not sure

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Give me an example

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I’ll multiply it

tight compass
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a/b * c/ d = ac/bd.

mental steeple
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Oh yea

tight compass
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That is how I got that up top.

mental steeple
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Right

tight compass
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Yes.

mental steeple
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Tanx?

tight compass
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Yes.

mental steeple
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huh but my teacher got 1 as the answer

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Want to see his work

tight compass
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Not sure how your teacher got 1, unless they evaluate tan(x) at x = pi/4.

mental steeple
tight compass
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Hmm 🤔.

mental steeple
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right I’m confused to

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I’ll ask him

tight compass
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Ok I don’t see anything wrong with his solution.

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I can’t seem to find anything wrong with ours.

mental steeple
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okay

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So both are right?

tight compass
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Checking again.

mental steeple
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👍🏼

tight compass
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@mental steeple I found his error. In the last line tanx from previous line is not equal to sin^2x/cos^2x.

mental steeple
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Yea I saw that to

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Not sure where he got the cos2x from

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And sun

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sin

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So we are right correct?

tight compass
mental steeple
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Nice I’ll tell my teacher about it rn

mental steeple
tight compass
mental steeple
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?

tight compass
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Like express it in terms of cos and sin.

mental steeple
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Ik that cot^2 = cos^2x/sin^2x

tight compass
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Yes.

mental steeple
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But idk what to do after

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For csc

tight compass
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What about csc^2(x)?

mental steeple
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1/sin^2x

tight compass
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Ok what do you do think we should do now?

mental steeple
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Divide?

tight compass
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Yes.

mental steeple
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2Cos^2x

tight compass
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Close.

mental steeple
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Bruh I just got that wrong on my test smh

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oh

tight compass
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It should be cos^2(x)/2.

mental steeple
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Oh

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dam I got that wrong lol

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It was that easy

tight compass
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Next time be patient and work it out first before asking for help.

mental steeple
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Just the 2 threw me off

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Otherwise it’s easy

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Also quick question if something was 1/cos^2x + sin^2x / cos^2x would that equal 1+sin^2x / cos^ 2x = cos^2x /cos^2x = 1

tight compass
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It follows from sin^2x + cos^2x = 1.

mental steeple
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Okay ty

spiral crescent
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you guys got a good math problem?

sterile steppe
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I need some help evaluating a problem(top of the page)
When I can evaluate it jn 2 different ways(right and left side) I just don’t which one is correct

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Btw I just graphed the angles at the bottom of each one

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This is the correct picture

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My bad

hushed sphinx
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Note that tanx=1 happens for x=kpi+pi/4, and those x also give sinx=±sqrt(1/2).

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However on the left-hand side you also get some spurious solutions caused by the squaring early on -- that is, x=kpi-pi/4 also gives you sinx=±sqrt(1/2) but don't satisfy the original equation.

sterile steppe
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I thought it was just positive

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oh wait nvm forget that

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ohhh ok this makes sense now

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thank you

umbral willow
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uh how does one find the intersect of 2 exponential functions

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google wont help me

hushed sphinx
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Set f(x)/g(x)=1.

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Or find the intersection of their logarithms.

umbral willow
umbral willow
velvet star
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question, how many point(s) does a tangent line intersects a curve of a function?

steel tulip
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Depends on the function

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Zero times to infinitely many times

hushed sphinx
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You need to figure out exactly what "intersect" means to you first. Of particular relevance: Does the point of tangency automatically count as an "intersection"?

sharp mist
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What does p represent in the way of graphing conics in polar equations represent?

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ep/1-ecos(theta)

ancient bloom
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Does anyone mind helping with a hw problem?

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this is the math problem

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when I factor it I get 131^2 k^2 t^2 -168t+48

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17161+k^2 t^2-168t+48

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my professor said I need to use the quadratic formula for this problem

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But I'm still very confused

viscid thistle
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Use the quadratic formula

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a=17161*k^2

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b=-168t

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c=48

brittle ice
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I need help with 63

willow bear
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@brittle ice do you still need help with this

brittle ice
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yeah

willow bear
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if $z$ is such that $p(z) = 0$ then what is $p(\bar{z})$?

obsidian monolithBOT
regal harness
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hello, Im confused on this question. Is there an identity to use or something?

drowsy elm
obsidian monolithBOT
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Eevee Trainer

willow bear
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i was addressing this question to jef

drowsy elm
drowsy elm
drowsy elm
gentle bolt
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is this all the topics that should be covered in pre-calc?

gentle bolt
ionic sparrow
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Hii can anyone confirm if this is correct

vapid plaza
ionic sparrow
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Oh

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The second one I think it might be is 2 because it matches based on the y-axis Bht it’s also similar the choice answer #1

ionic sparrow
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Like it could be choice two but idk the difference between choice 1 and 2

vapid plaza
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You need to know the difference between (i) and (ii).
In (i) x approaches -4 from the left
In (ii) x approaches -4 from the right

tight compass
quick harbor
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Need some help, I can send an image of the work

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Domain and range of relations and functions

vestal rock
flat falcon
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Hello, I wanted to know what I should know to start deriving functions?

crisp palm
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great series to watch to help understand calculus

full pagoda
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differentiate

crisp palm
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oh

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derive differentiate

vestal rock
crisp palm
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i am an idiot

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🗿

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i READ IT WRONG

full pagoda
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no i'm pretty sure you interpreted it correctly lol

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i'm like 98% sure they meant differentiating

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but everyone always says deriving

obsidian hinge
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^^^

vestal rock
full pagoda
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deriving does not mean differentiating lmao

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if you know calculus you should definitely know that

vestal rock
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ik

vestal rock
crisp palm
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but yeah

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did they mean derive or differentiate

vestal rock
rare canyon
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Hello, I'm in need of help for a differentiation proving question I'm stuck at, I can send the question and what my working is so far, hoping someone could help me with where I went wrong/where I'm stuck at?

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At the side it says k is a constant

uncut mulch
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where's

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coming from

rare canyon
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is that how I'm supposed to differentiate x²k?

uncut mulch
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no

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how exactly are you getting that for the derivative of x^2*k

rare canyon
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Product rule

uncut mulch
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show in full detail

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i don't want to keep asking how you did...
every time

rare canyon
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Ack... That's all I wrote man, I'm not even sure what I'm doing so...

uncut mulch
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how exactly did you apply the product rule?

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it looks like you skipped stuff and./or didn't apply it properly

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and also applying product rule to this is a bit overkill

rare canyon
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like the whole equation, I'm supposed to use quotient rule to differentiate it, right? So I took the denominator multiplied by the first derivative of numerator,

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but am I not supposed to use product rule to differentiate x²k?

uncut mulch
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well to differentiate you fraction you could apply the quotient rule
but the issue with what you did is that you didn't differentiate x^2*k properly

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you "can" apply the product rule if you want, but you'd need to apply it properly

rare canyon
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oh wait

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k is a constant

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so it's essentially kx² right?

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damn I didn't need to use the product rule

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nvm I get it now, thanks for the help!!

viscid thistle
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hi

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i need help

hushed sphinx
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That's not PREcalculus

viscid thistle
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ok

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sorry

pallid summit
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Although it's differential stuff, I am happy to help. Why don't you try to differentiate it partially,if you know. Otherwise, I can give you a solution. I think the answer is a set of points which satisfy the condition above.

viscid thistle
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i already did it now

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its -2,2, 2,-2

pallid summit
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Good to know

viscid thistle
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thanks

pallid summit
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No problem:)

short saddle
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$P(X)$ is a real polynomial such that $P(X+1)-P(X)=X^{2022}$. Prove that $P(2/3) \geq P(0)$.

obsidian monolithBOT
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erictheeonicpizhao

vale escarp
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how do i do this?

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<@&286206848099549185>

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do i find the magnetitude of each vector?

steel aurora
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What is it asking for

vale escarp
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it diodnt specify

uncut mulch
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these look like nested combinations/binomial coefficients

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just evaluate

blissful stone
rare canyon
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nah

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was asking about proving

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it's resolved now so

blissful stone
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alr

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I should begin doing some precalculus in the nearest future

short saddle
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To locate a whale, two microphones are placed 6000 feet apart in the ocean. One microphone picks up a whale's sound 0.5 second after the other microphone picks up the same sound. The speed of sound in water is about 5000 feet per second.

a. Find the equation of the hyperbola that describes the possible locations of the whale
b. What is the shortest distance that the whale could be to either microphone?

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ig draw a diagram but i can't visualise

short saddle
fair cave
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ok could ya get the diagram?

short saddle
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i'm literally going to sleep

cursive estuary
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ok so 😂 how tf do u do this 😭 maybe im just not getting it but why is the f(x)= equation so huge ??

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this is an example I got from trying to solve a hoemwork questions but I don't understand the instructions

hybrid pewter
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so 18/(4x^2 + 5) is case (1) where the degree of the numerator is less than the degree of the denominator

chrome haven
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A spherical zorb with a radius of 1.5m is being filled with water at a rate at 100π cm^3/s. At what rate is the height of the water increasing when the water is 20cm high??

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Need HELP!

rocky wind
chrome haven
median oasis
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i believe the area of the circle in at 20cm is .56pi m^2

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or 56 pi cm^2

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and (100pi cm^3/s)/(56pi cm^2) = 25/14 cm per second

median oasis
viscid thistle
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woah

median oasis
viscid thistle
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your handwriting is terrible

median oasis
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i cannot zoom

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it's hard

viscid thistle
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from what i gather the radius is 1.5

median oasis
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i was writing on notes on my phone 😆

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i am talking about radius of the circle cross section

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at the waterline

viscid thistle
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the length of the chord?

median oasis
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idk damn know

viscid thistle
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ok

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sure

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use pythagorean theorem

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and then double your answer

median oasis
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🤨🤨

haughty robin
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can someone help explain this?

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idk which quadrant im supposed to go to

stable yacht
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Besides that being a very recognizable ratio, the interval of [0, 2π) is nothing special.

haughty robin
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ik your supposed to find the inverse

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but how do i know which quadrant to go to

stable yacht
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What do you mean by which quadrant? You mean to physically draw the triangle?

haughty robin
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no, after you get the inverse you are supposed to figure out what quadrant it came from

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cos^-1(4/5) = 0.64

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then you need to find the reference angle

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but idk what quadrant equation for reference angle im supposed to use

chrome haven
median oasis
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ru sure

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it should be 100/56 cm

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or 1/56 m

median oasis
thin raft
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Why does partial fractions fail sometimes?

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E.g. $\frac{1}{(x^2+4)^2}$

obsidian monolithBOT
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AstroRP

thin raft
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How do I partition this?

willow bear
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you can't, unless you're willing to go into complex number shit

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this is already an elementary partial fraction though

thin raft
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because wolframalpha doesn't show anything (real or complex)

willow bear
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$\frac{1}{(x-2i)^2(x+2i)^2}$

obsidian monolithBOT
willow bear
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,w partial fractions 1/((x-2i)^2(x+2i)^2)

obsidian monolithBOT
willow bear
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it gets something done

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i guess you'll end up with complex logarithms which are going to be hell to work with

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but it gets something done

thin raft
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ah nice ty

mellow tapir
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Friend was doing sequences, find explicit formula

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$\frac{-6}{5}, \frac{7}{15}, \frac{-8}{45}, \frac{1}{15}, \frac{-2}{81}, \dots$

obsidian monolithBOT
#

! Brontochad (RYC4blushysully)

willow bear
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...19, 19, 19, 19, 19, ...

mellow tapir
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Turns out if you write the bottom as a geometric sequence it works super nicely

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1/15 = 9/135 so it continues the arithmetic sequence on top

vagrant crown
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hello

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i am new

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i was bored today so i made piecewise functions with a single equation

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it doesn't support >=, <=, =, or != in the domains though

median oasis
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one time i made a penis on desmos

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and i also made a person

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👍

willow bear
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{condition1: formula1, condition2: formula2, ...}

steel fern
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So I'm solving the problem 9x^2-6x+7=0

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The actual answer is 1/3 ± √6i/3

willow bear
#

some of the issue appears to be in your handwriting, which messes up the equation(s) you're working with

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also plugging things in incorrectly in some places

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just in the first line alone:

  1. why does the -b term appear not to be part of the fraction? the fraction bar should extend clearly to cover it.
  2. the stuff under the root is b^2 - 4ac, which in your case should be 6^2 + (-4)(9)(7), not 9^2 + (-4)(9)(7) as you wrote.
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it all went downhill from there

steel fern
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lol
ok

steel fern
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Where am I going wrong @willow bear

willow bear
#

you have literally not fixed the very things i just mentioned to you

steel fern
#

Hold on

steel fern
#

I didn't see it lol

willow bear
steel fern
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Oh so I'm just an idiot who's doing math at 4 am

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Ok

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Lol

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Sorry

willow bear
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why are you doing math at 4 in the morning

willow bear
#

quiz?

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we won't do your homework for you.

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ok then posting this here is pointless

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everyone here has their own problems to deal with

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nobody gives a shit about yours

median oasis
supple owl
#

war was here

willow bear
#

"a discord trans"

grizzled orchid
#

b&

willow bear
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thank you

supple owl
#

guys can you reminde me by the binomial theorem ?

willow bear
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$(x+y)^n = \sum_{k=0}^n \binom{n}{k} x^{n-k}y^k$

obsidian monolithBOT
supple owl
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$what do \binom{n}{k} mean$

obsidian monolithBOT
#

MRme001

willow bear
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binomial coefficient, a.k.a. "n choose k"

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$\binom{n}{k}$ is defined as $\frac{n!}{k! (n-k)!}$

obsidian monolithBOT
supple owl
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thanks

pale solstice
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in the function 4/(x^2+x) why is there a graph under the x axsis?

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i understand that x goes to ifinity when x approches -1 from the left and 0 from the right

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i think it is because x is defined between -1 and 0, should i take the derivitive and look for when the derivitive is 0 to determent when x is defined between -1 and 0 ?

willow bear
pale solstice
willow bear
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do you mean the highest point of that part?

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if so then yes

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...your phrasing is hard to parse

pale solstice
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yes

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yea im not the best with either math terms and explaining math in english, but thanks for the help!

final saddle
#

that's a reciprocal of parabola

pale solstice
final saddle
#

and loc min will become loc max

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hence the "max point" of that particular part

final saddle
final saddle
pale solstice
willow bear
final saddle
#

fixed

silk fjord
#

⬇️ sus

valid parrot
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I don’t know how to prove this, can someone help ?

median oasis
#

i don't think that's precalc

dusky bramble
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If you multiple the square root by M
the M^2 is canceled out, leaving you with

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$\sqrt{P^2+4\cdot{pi^2}\cdot{n^2}\cdot{M^2}}$

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and as M approached infinity, this entire expression does the same

obsidian monolithBOT
#

Deus_Vult

steel fern
steel fern
#

Ok

onyx gorge
#

i guess it applies to any math, but i’m in precalc rn.

does undefined = undefined? or does it not equal anything bc it’s… undefined

astral apex
#

technically the word 'undefined' has no business showing up in a proper equation

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but people do it all the time in math classes and it's understood what they mean

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like there will be a function, say f(x) = 1/x

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and people will write "f(0) = 1/0 = undefined"

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what they really mean is f(0) is undefined

vapid plaza
#

1/0 “is” undefined, but not that 1/0 “is equal to” undefined

astral apex
#

right

onyx gorge
#

so it popped up in that context

astral apex
#

cot(pi) is undefined

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sometimes people may write cot(pi) = undefined, which is sloppy, but it's generally understood

onyx gorge
#

wait let me write out what i remember

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cos^2(pi) * cot(pi) = cot(pi)

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would those two expressions equal each other?

astral apex
#

I see

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I mean, both sides are undefined

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I see the point is you can erase cos^2(pi), since it's 1

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but you could even just say "cos^2(pi) * cot(pi) is undefined" and stop there without using an equation

onyx gorge
#

would they equal each other though

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that’s all i’m worried about because my math core was on that

#

same exact problem

astral apex
#

I assume they mean for you to say yes

onyx gorge
#

OH THANK FUCK

astral apex
#

kind of a sketchy problem though

onyx gorge
#

yea i may have solved it wrong but i checked it over twice

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unlikely but very much possible

opaque berry
#

is precalc hard learning it for the first time? I'm in algebra 2 right now and I hear it's like a whole new concept in math so I wanteed to hear other people's opinions on it

obsidian hinge
#

nah it's not bad

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precalc is pretty easy

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calc is the first bit of real actual math you get to see

opaque berry
#

algebra 2 or precalc which one do you think is harder learning for the first time

astral apex
#

I mean

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if you ask me, it's all the same shit

obsidian hinge
#

equal tbh

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precalc builds off algebra 2 just like algebra 2 builds off algebra 1

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again, calc is where you first see math

opaque berry
#

alr cool thx

astral apex
#

precalc has the unit circle and common trig values, it can be a lot to take in

obsidian hinge
#

trig makes sense as an extension

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he'll be fine

#

it's not bad

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as long as you understand em

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and why it works the way it does

astral apex
#

agreed

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but that's easy to say when you do understand it 🙂

obsidian hinge
#

hm fair

opaque berry
#

i don't remember anything from trig because it was during quarantine and I was playing valorant during all the zoom classes...

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damn

astral apex
#

some students find all the factoring degree 4 polynomials and crap from algebra 2 harder than anything in precalc

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really depends on what you're stronger in

obsidian hinge
#

gods i forgot we had to do that lmfao

opaque berry
#

im good with the polynomial stuff i think

onyx gorge
#

learning sines, cosines, csc, and all that jazz is like learning a new language but once you get the hang of it, it’s super easy

opaque berry
#

👍

astral apex
#

it's a chore

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you have to guess a root by the rational roots theorem

onyx gorge
#

is fifth degree polynomials in precalc?

astral apex
#

not really, but algebra 2

onyx gorge
#

i do not remember learning that in alg 2

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oh wait, p’s and q’s and synthetic division?

astral apex
#

they even do descartes' rule of signs

opaque berry
#

i wish i'm that one kid in the back of class that pays no attention in class and is always watching youtube videos in class but still somehow knows all the math and is a genius

astral apex
#

it's done because you have to guess a root, and you might get unlucky and not try the right one until the last possible one

opaque berry
#

lucky

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what are you learning rn

onyx gorge
#

precalc

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calc ab junior year and bc senior year

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assuming i pass the classes

opaque berry
#

same for me

astral apex
#

possible but would take some trial and error

opaque berry
#

i dont even know anything about calc but i already hate it

onyx gorge
#

my friend’s taking it rn and she said just know the unit circle by heart

rose basin
#

Basically this question asks me to find the vertical intercept and I'm wondering if I solved it properly using this equation that I did here.

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Answer is b = 8,000

hushed sphinx
#

Is the second of your images part of the problem or your answer?

rose basin
#

Part of the answer

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It's just what I did to find my answer

hushed sphinx
#

Can you state a concrete formula for profit as a function of items sold?

#

Plug 2000 and 3000 into that and verify that you get 24000 and 32000 out.

rose basin
#

Yeah it works

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I was able to solve the problem

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Thanks

viscid thistle
#

Learn quadrant one, there are three values, 1/2, sqrt 2 /2 and sqrt 3 / 2

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the pi values in quadrant 1 are more obvious on inspection. Add pi to move half a unit circle to quadrant 3, add pi/2 to move a quarter a unit circle to quadrant 2

onyx gorge
#

true true

karmic zephyr
#

brooo

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its 1am

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and i just got to vectors

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and this shit is tripping

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like, why i gotta find out how to represent it in how many one unit movements it made

willow bear
#

you don't "gotta" do shit if you're so repulsed by it

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but this is the decomposition of a vector in the standard basis

#

and especially in linear algebra one is often interested in looking at vectors through a different basis than the standard one

#

to say it in a highly abridged manner that skips over most of the details

karmic zephyr
#

not repulsed, just dazed and confused xD

fringe raft
# karmic zephyr

because think of the cartesian coordinates as an incomplete quantity and you want something to tell you about the direction of functions and curves

hollow elk
#

what are all the topics i have to learn before studying precalulus?

hollow elk
#

i learned trig

#

what about exponentials

#

are polynomials used in precalc?

#

how

#

ok

#

how advanced should my polynomial skills be?

#

what does 3rd degree include eg. algabraic geometry

#

simplifying dividing and multiplying then i can move on to precalculus?

#

ok thanks i might be able to do that in a couple of days

#

no prior knowledge tho

#

possibly

#

thanks

#

ik what to study now

tired pilot
#

I have this complex analysis problem but I'm pretty sure it's just a geometry/precalc problem about hyperbolas. I have $z\in\mathbb{C}$ where $z-1=r_{1}e^{i\theta_1}$ and $z+1=r_{2}e^{i\theta_2}$. I need to show the region described by the conditions $r_1 > 0, 0 < \theta_1 + \theta_2 \leq \frac{\pi}{2}$ is the region between the unit hyperbola $x^2 - y^2 =1$ and the x axis in the first quadrant. I'm stuck showing how z satisfying the constraints involving $r_1$ and $\theta_1 , \theta_2$ imply z is in the region described above, I think I see how to show the opposite inclusion.

obsidian monolithBOT
#

DootDooter

tired pilot
#

Geometrically we should have something roughly like this:

#

The last thing I could think to try was to solve for z in terms of $r_1,r_2,\theta_1,\theta_2$ and then try to sub into $x^2-y^2\geq 1$ looking for some nice angle relationship.

obsidian monolithBOT
#

DootDooter

tired pilot
#

That got me here:

#

Assuming I didn't make some super dumb algebra or trig mistake, which I might have because my brain is currently kinda fried.

#

But I don't see any nice relationship that is useful from here. If anybody sees any way to proceed ping me.

#

Wait maybe I see it

#

$z+1-(z-1)=2$ so $r_2 cos(\theta_2) - r_1 cos(\theta_1) = 2$ also. So, $r_1 r_2 cos(\theta_1+\theta_2)\geq 0$.

obsidian monolithBOT
#

DootDooter

tired pilot
#

Pretty sure picking theta one and two in the interval I need and reversing my steps in that last image will get me the identities that I need. pandaWow

misty gulch
cedar harness
#

ok sorry

misty gulch
bronze pendant
#

hey guys do you mind helping me with the one i got wrong? (i got my answer for the 1st one by doing <340cos40, 340sin40> )

willow bear
#

the wind is blowing southeast while your vector is pointing east

spring tendon
#

$$ \begin{aligned} &y \geq-2\ &y \geq x+3 \end{aligned} $$

rose basin
#

Anyone here know how to solve this problem? I don't understand how to solve it.

abstract lodge
#

so take ln of both sides

#

look at the top example

#

so u can just ln both sides and isolate x

rose basin
#

Alright thanks for the help

hollow elk
#

i am gonna study logarithms

#

i am a begginer but i do however know the very very basic concept such as what the function does

#

could someone give me recommendations on what to learn

abstract lodge
#

like use khan academy or some other source to learn basic algebra then move on from there

safe stump
#

anyone have other alternative step-by-step solution without prior knowledge of L'Hospital Rule?

#

I want to know why that limit become natural logarithm, using theorems and such

#

zoomed in graph can show me the value, but still not satisfied with that one

tight compass
# safe stump anyone have other alternative step-by-step solution without prior knowledge of L...

This is what they had. We have an indeterminate form of 0/0 when we take the limit as x->0. So taking the derivative wrt x for the top and bottom of (2^x - 1)/x we have it's ln(2)2^x. Now take the limit as x->0 we have it's ln(2).

As for an alternate proof, maybe graphing the function in desmos and zooming in to seem what values it's you think it's converging to and the using the definition of a limit to prove the function converges to that.
I can't think of anything else right now.

safe stump
# tight compass This is what they had. We have an indeterminate form of 0/0 when we take the lim...

Have done with graphing proof and i saw the irregular shape after zoomed in the graph. However, the algebraic solution that u told me or from the pic above is kinda recursive. I just curious whether there is algebraic way to solve it without prior knowledge of derivative itself. Assume that equation is just an algebraic equation and as a people without calculus knowledge, i want to solve it just using algebra

viscid thistle
#

I need help one those two questions please

safe stump
#

Maximum means something with differential. Open your book

#

for 9a, use the limit definition of derivatives and the derivative law of trigonometry

viscid thistle
#

Those are the two types?

#

One with limit deriv and the other one is with trig

safe stump
#

yeahh what else do u think??

viscid thistle
#

Ohh I got it

safe stump
#

if you know what is sec(x) means, then everrything's trivial

viscid thistle
#

I understand now

#

Thank youu!!!

safe stump
#

ur welcome

sonic merlin
#

let's say I start investing 160 dollars at the start and i don't add anymore money and every week I earn 5% profit, what's the equation for this scenario?

woven valley
#

160(1.05)^w where w is every week after investing that 160

#

Pic unrelated

#

Oh wait

#

Are we reinvesting this money

#

“Compounding interest”

#

If we are then the equation above is fine

hushed sphinx
#

If you're offered an investment that will give you 5% profit each week, it's a scam, no ifs or buts. Run.

sonic merlin
woven valley
#

Bruh=moment

sonic merlin
#

i was curious

#

thanks

sonic merlin
woven valley
#

Yeah we’re good then, the standard form for compound interest would be a(b)^t where a is the original investment, b is the increase (this number should always be greater than 1 to represent an increase) and t represents integer unit for measuring time, like 2 weeks or 5 months.

lucid current
#

can i get a quick rundown on why a certain thing is the way it is? I'm in calculus but ive completely forgotten about sin, cos and tan related stuff

#

i cant remember how to actually reach this result

astral apex
#

apply arctan to both sides

honest gorge
#

Real quick I was wondering if I did this problem right

#

Trying to find the vertex

astral apex
#

the way you take minus signs out of the parentheses is no good

honest gorge
#

Wait why isn’t a negative leading term

astral apex
#

I mean you go from

#

$(-x^2 + 4x) - 5$

#

to

obsidian monolithBOT
#

ManifoldCuriosity

astral apex
#

$-(x^2 + 4x) - 5$

obsidian monolithBOT
#

ManifoldCuriosity

astral apex
#

when you take out a minus sign in situations like this, you have to flip the sign of everything inside the parentheses

honest gorge
#

Oh I did that

astral apex
#

oh I see, you do it in the next step

#

just so you know, the equation where you didn't do it yet is technically wrong

honest gorge
#

So I should do it early?

astral apex
#

in one step

#

$(-x^2 + 4x)-5=-(x^2-4x)-5$

obsidian monolithBOT
#

ManifoldCuriosity

astral apex
#

but ok, you do get there

#

but then you have another problem

honest gorge
#

Oh okay but I dont think I solved it correctly

astral apex
#

you correctly write + 4 inside the parentheses

#

but then you balance it with -4 outside

#

which would be right if it weren't for the negative sign in front of the parentheses

honest gorge
#

I did that because -4/2^2=4

astral apex
#

that part's good

#

it's the (-4) you wrote after the parentheses

honest gorge
#

I thought we do that to both add the -4 to both sides

astral apex
#

that minus sign in front of the parentheses means you're really doing -4 to your expression

#

so you have to balance that with the opposite, +4

#

should be:

#

$-(x^2-4x+4)+4-5$

obsidian monolithBOT
#

ManifoldCuriosity

astral apex
#

now somehow you do end up with -1 below that

#

which is right

#

but it doesn't follow from what you wrote

#

in the end your answer is right

#

but the work has several mistakes

honest gorge
#

I had double negatives I wrote -(-4)

#

-5

astral apex
#

ohh

#

ok I see it

honest gorge
#

So I got the right answer but my steps are confusing?

astral apex
#

yeah

honest gorge
#

Alr I’ll fix it

astral apex
#

you seem to know how to do it, just not written up in a usual way

honest gorge
#

What if I did it by equaling the equation to 0

astral apex
#

you can do it all the same way

honest gorge
#

Ok Alr Ty

astral apex
#

sure thing

honest gorge
#

Is this better?

astral apex
#

fixed some things, but you forgot about x for a few lines

#

you wrote x^2 - 4 + 4 in the parentheses

#

instead of x^2 - 4x + 4

#

also you should have a + before your 4 after the parentheses

honest gorge
#

Can someone explain this to me?

uncut mulch
#

what have you tried?

#

do you know the intermediate value theorem

honest gorge
#

No

uncut mulch
#

consider looking it up first

honest gorge
#

Okay so I have to substitute both values in the equation?

uncut mulch
#

yes, (separately)

honest gorge
#

This is what I got

#

Wait but they are both negative so is there no zero?

viscid thistle
#

There is a zero, it goes down, then stop, then goes down

honest gorge
#

Yeah I’m confused now

#

There’s no number between -3 and -4

grand vigil
#

help

#

<@&286206848099549185>

viscid thistle
uncut mulch
#

Wait but they are both negative so is there no zero?
not necessarily, depending on the function, there could be a zero in the given interval
the IVT can't be used to conclude that there no zeros

#

so in this case since both are negative, IVT cannot be used to determine if there's a zero in that interval

grand vigil
#

plshelp

stable yacht
#

And you have an altitude.

grand vigil
#

hm

civic sierra
honest gorge
#

A little bit

#

But didn’t go into detail

grand vigil
#

wait i will give a sum it's impossilbe to do

civic sierra
honest gorge
#

I have but it’s really confusing to me

uncut mulch
#

if the signs were different, IVT guarantees that there will be at least one zero
otherwise it doesn't do much

#

the IVT can't be used to conclude that there no zeros
so in this case since both are negative, IVT cannot be used to determine if there's a zero in that interval

civic sierra
#

You'd have to show that there exists/doesn't exist a zero using derivatives, I can't think of another way

honest gorge
#

This is the example that was given

#

Wait wrong one

#

This is it

civic sierra
#

Do you have an example where the signs are the same?

honest gorge
#

This is the only one that was given

civic sierra
honest gorge
#

Oh okay alright Ty

viscid thistle
#

I need help please

stable yacht
viscid thistle
#

can i have help pls

agile sable
#

Can you be more specific?

viscid thistle
#

all the answers that i entered are incorrect

stable yacht
#

C is incorrect simply because (0, 2) falls on the circumference of a circle with a center at (2, 2) and a radius of 2.

#

It also looks like D is not asking what it intends to ask. Your answer is correct, but I think there might have been an error with the question.

agile sable
#

Do monsters have width?

hushed sphinx
fast monolith
#

Can I borrow some help to get this started please?

fallow quiver
#

The objective starts from y = h_0 and ends up at y = -h_0 finally again, when that happens it's finally not in air.

#

Use those facts.

glacial mirage
hazy dust
#

hey this one has been driving me bonkers, i think i have to use implicit dif/related rates but i’m losing my mind some help would be appreciated

willow bear
#

would you like the slightly cheaty but legit solution, or the solution your teacher likely expects from you?

hazy dust
#

both would be good to be honest

#

i’d like to learn the proper solution but seeing the cheaty solution could help speed me up on an exam

willow bear
#

cheaty: the radius and height of your cylinder are given by r(t) = 5 + t and h(t) = 8 - 4t, and the volume is V(t) = pi * r(t)^2 * h(t) as you wrote. in all this, t=0 is the moment in time that is of interest to us. your goal is to find V'(0), which you can do by expanding out V(t) and applying little more than the power rule.

#

'proper': same thing except you differentiate V wrt t symbolically, treating r and h as functions of t (which they are) and ending up with a mess of r, h, dr/dt and dh/dt into which you then plug the numbers. no mention is made of any specific point in time

hazy dust
#

ah thank you

#

i think my mistake was not interpreting r and h as functions of t

#

which totally makes sense now but i just got confused since the usual style of questions doesn’t normally give 2 values (ie radius and height) and couldn’t figure out how to apply it

#

cheers man 🙂

viscid thistle
#

Why do we turn terms into smaller with '

#

like

#

x' = (x - 1)

#

whats wrong with x -1 ?

agile sable
#

X-prime, as its called is a way of saying its different but similar to x

#

x = (x - 1) isn't valid

vapid plaza
#

It’s all a matter of notation
x’ is just a symbol or letter used in math, similar to a or b

#

And it meaning in use depends on context:
In calculus it usually means the derivative of x
In other places it probably just means the new value of x after some change

chrome scarab
#

Hey can someone help me with rhis question?

#

The second pic is my try

chrome scarab
#

<@&286206848099549185>

shut jewel
# chrome scarab

uhm sry but what is the question asking? I dont really comprehend this

hazy dust
#

i’ve been given a relation and am calculating the dy/dx using implicit, but it is asking for it in terms of s only how do i find without y?

#

find dy/dx in terms of only x

#

that’s what i got

#

<@&286206848099549185>

past meadow
#

sorry for the late response, but you can solve the implicit equation for y explicitly since y>0

#

@hazy dust

#

Then, you can either take the derivative of that directly, or substitute what you got for y into the implicit derivative you've already found.

tranquil haven
#

How would I differentiate this?

#

I need to get a general formula for displacement based on gravity and it's altitude

#

$\rho(t)$ needs to be substituted later based on the position then

obsidian monolithBOT
#

sentinel

stable forge
#

Could someone help me with my last few problems, there’s some proving Identitys, a double angle problem, and a few other things

willow bear
#

@stable forge don't ask to ask, just post your problem(s) that you need help with

rocky wind
obsidian monolithBOT
#

vin100

hot reef
spiral locust
#

What I do

stable yacht
#

What question are you asking? That is just an expression.

mental steeple
#

Can anyone help me I have to verify the identity

patent beacon
#

There's only sin/cos on the left, so convert everything to sin/cos on the right

mental steeple
#

This is what I did ignore the cos/1 in second step

full pagoda
#

why'd you turn sec^2(x) into cos^2(x)

onyx gorge
#

sec^2(x) is equal to 1/cos^2(x)

mental steeple
#

Okay

#

So 1/cos^2x/sin^2x/cos^2x-1?

#

@onyx gorge

onyx gorge
#

yes that’s good

#

now for the denominator, combine the two terms by transforming the 1

mental steeple
#

Wdym

onyx gorge
#

you have this in the denominator right?

mental steeple
#

Yes

onyx gorge
#

you need to somehow combine those two terms

#

so find a common denominator

mental steeple
#

Cos2x

#

?

onyx gorge
#

just cos^2(x)?

#

oh wait

mental steeple
#

I think

onyx gorge
#

yea cos*2(x) is the common denominator

#

so how would that effect the 1

mental steeple
#

It would be 1/cos2x

onyx gorge
#

does 1/cos^2(x) = 1?

mental steeple
#

no

onyx gorge
#

so how could you change the 1 so that the denominator is cos^2(x) and would still equal 1

mental steeple
#

Can’t you do cos2x/1 then cross multiply which the cos2x cancels out then your left with sin2x-1 which equals -cos2x

onyx gorge
#

you mind writing out the work and taking a picture of that?

mental steeple
#

ok

onyx gorge
#

my mind is dying

mental steeple
#

@onyx gorge

onyx gorge
#

gasp

#

no

mental steeple
#

:(

onyx gorge
#

would you ever do this?

mental steeple
#

No

onyx gorge
#

same concept, you can only cross out if it’s multiplication

mental steeple
#

So we are subtracting right

onyx gorge
#

yea

#

no multiplication

mental steeple
#

How do I do it though

#

idk how to subtract it

onyx gorge
#

lookey

mental steeple
#

Oh I was thinking of that didn’t know I could do that

onyx gorge
#

it’s way harder to figure out sometimes because it’s letters and not numerical

#

yea, that’s valid

mental steeple
#

So do I subtract scrips

#

across

onyx gorge
#

yes yes

mental steeple
#

Wouldn’t the top =1

onyx gorge
#

sin^2(x)-cos^(x)/cos^2(x)

#

nah. that’s sin^2(x)+cos^2(x)

mental steeple
#

After subtracting

onyx gorge
#

yep, for the denominator of the entire expression

mental steeple
#

where did you get cosx

#

Isn’t it cos2x

onyx gorge
#

i may have typed it wrong

#

let me write

mental steeple
#

Ok

onyx gorge
#

and now it’s just division!

mental steeple
#

-cos^2x / cos^2x = -1?

#

Sin^2x/cos^2x = tan ^2x

#

tan^2x -1?

onyx gorge
#

don’t over think

mental steeple
#

what where did you get the 1/cos^2x

onyx gorge
#

the original equation

#

sec^2(x)

mental steeple
#

ohh

#

Yes I didn’t see that

#

Lol

onyx gorge
mental steeple
#

Thank you

onyx gorge
#

divide, cross multiply, and you get your answer

#

don’t be afraid to convert

mental steeple
#

Got it

ebon barn
#

I’m confused on relative maxima and minima

#

I just started summer precalc btw

onyx gorge
#

what the kronk is that?

ebon barn
#

It’s just saying if the graph is at a relative minimum or maximum

young peak
#

yow just a simple question, is integration the inverse process of differentiation or the reverse process?

#

dunno if reverse and inverse are the same

heavy sonnet
#

I don't think reverse is a formal description

#

They're inverse operations

#

Though they take functions as parameters not singular number.

#

(although a constant could be thought of as a function that returns the same number independent of the input)

viscid thistle
#

Is it always the case that if g(f(x)) is one to one this implies f(x) is also one to one and it g(f(x)) is onto then this implies g(y) is also onto? Prove whether the statement is true or not

stuck lark
#

@viscid thistle if u agree then prove it, if not give a counterexample

viscid thistle
stuck lark
#

u can try getting an idea of whether its true by playing with examples

#

if ur proving, it helps to unpack definitions (in this case those of 1 to 1 & onto)

clever gazelle
#

Someone can help me with this problem
-3x(2x+3)>-(-3+4x)

worthy idol
ebon barn
#

Should I factor when simplifying

#

Just look at the last two lines

#

The answer key says I don’t need to factor out the h but I feel like I should

#

I mean, doesn’t that make it…simpler?

stable yacht
#

It depends on what you are doing with it.

#

If you are finding zeroes, trying to factor saves you time over the quadratic formula.

#

Especially if one of the zeroes is 0.

gritty crane
#
  1. Let "F" be a function of Real variable, defined by f(x)=mx+b /(this bar means such that) 2f(2) + f(4) = 21 and f(-3) -f (1 ) = -16. Find 1/3 f(1)
  2. If f(x) = ax^2 +bx +c ; f(-1) +f(1/2)= 15/4 ; f(-1)=0 ; f(1) = 8 . Find f(5)
ebon barn
#

But yeah I get what you’re saying it would definitely be smart to factor if you are doing pretty much anything with it.

stoic crater
bitter drift
#

Oh we just did that topic

#

Any questions?

stoic crater
#

Does anyone know why they use the cross product of u and v

#

Instead of v and u

stoic crater
bitter drift
#

Bcz Matrixes are non commutative

#

So the order you multiply them matters

stoic crater
#

Oh

#

But then how would a person know which is the correct order?

bitter drift
#

I think you have learnt This right r.n - a.n

#

Where r is your general point and n is the normal vector

stoic crater
#

what is an?

#

a is a specific point, right?

bitter drift
#

Yh

plucky slate
#

sin^2 x = sin x^2 ???

old isle
#

that is an identity

#

not an equation

#

every real number is a solution to that

#

oh wait

#

sin^2x and sinx^2 are the same thing right?

#

unless you mean sin(x^2)

stable yacht
#

,,sin^2(x) = sin(x)^2

obsidian monolithBOT
stable yacht
#

I think that was what was being asked. But it is a bit confusing when you don’t use parenthesis for the argument of sin.

raw python
#

$\frac{a - bx - 16}{\sqrt{3}x(\sqrt{a - bx} + 4)} = \frac{a}{\sqrt{3}x} + \frac{-bx}{(\sqrt{a - bx} + 4)} + \frac{-16}{(\sqrt{a-bx} +4)^{2}}$

obsidian monolithBOT
#

texaspb

raw python
#

is this expansion correct?

viscid thistle
#

no

#

i dont think so just by looking at it you can add all those and get a common base from those partial fractions

obsidian monolithBOT
#

Preetham

viscid thistle
#

can someone help me w this

slate reef
#

,rotate

#

oof

obsidian monolithBOT
slate reef
#

uuh I don't get it
why is there 2 prices of apple pies

viscid thistle
#

no clue:(

slate reef
#

@viscid thistle hmm I think i understand now

#

so

#

f(p) has linear relationship therefore it is in the form ax + b

#

a and b are constants and x is the amount of pies bought

#

if you substitute those values given you get a system of equations

#

3000 = 500*a + b
2300 = 325* a + b

#

and then you solve for a and b

viscid thistle
#

ohhhh

slate reef
#

in this case a will be the price of each unit of pie
and b will be a constant that means something like "the price of starting the production of pies"

viscid thistle
#

omg thank u sm u are a lifesaver

slate reef
#

you are welcome!

winged spire
#

i cannot figure out sum and difference formulas for the life of me

#

and manipulating sin/cos waves, will post an example soon

#

If someone knows a trick to look at them differently, but i cannot figure out the proper way to break down cos(x) into a sum and difference formula to solve it

lone tendon
#

Anyone how to find all solutions for the following equation: sin(-3x)=0.5? Only found one solution so far which is: (2*pi/3)n + 7pi/18

slate reef
lone tendon
slate reef
#

but thats only for the first lap around the circle

#

so your answer in this case should be
x = -pi/18 + 2*n*pi (n is natural)

#

the other solution is when -3x = 5pi/6

#

that also contains the + 2 n pi

lone tendon
#

ooh ok

brave heron
#

Who can find the general term for this serie

viscid thistle
#

le haut c trop compliqué pour comprendre

#

mais en bas je crois que c 48 et après 192

viscid thistle
viscid thistle
past meadow
#

For the first one, you'll notice that the numerator is a factor of the denominator

#

so if you can factorise the denominator, the numerator should cancel and you might be left with something cleaner

#

something similar is true for each of the rest.

inner copper
#

someone pls help it’s related rates

plain sable
inner copper
#

they didnt attach a diagram unfortunately

plain sable
#

Oh ok

plain sable
#

Try this.

#

I forgot to substitute r=d/4 in the final result u can do that and check…

low slate
#

How would I solve the top equation, can someone please help with this I’m stuck with what identities I need to use

#

<@&286206848099549185>

fast oxide
#

,rotate

obsidian monolithBOT
fast oxide
#

sin(x+y)/cos(x)sin(y)=1+cos(x)tan(y)?

viscid thistle
#

Question on Set Theory and describing Rational Numbers (it’s in my pre calc text, apologies if this should be asked elsewhere).

vivid void
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which is incorrect

viscid thistle
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So thr first line is incorrect and my second line is correct?

vivid void
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yes

viscid thistle
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That is disconcerting. The first one is how it’s written in my text. The second is what made more sense to me.

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So now I wonder how much else is wrong in thr textbook

low slate
tawny dirge
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how do i solve this

low slate
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I’m not sure the identities I need to use @fast oxide

slate reef
# tawny dirge

if you put this imaginary number in polar form you can do it easily

wooden lily
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I am not sure on how to solve this question. can anyone help me?

viscid thistle
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f(α+β)=tan(α+β)

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Using the figures, tanα = -1/x and tanβ = -3y

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Then you can simplify to get the final answer

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Oh wait

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tanα = 1/sqrt(3) and tanβ = -2sqrt(2) (since x=-sqrt(3) and y=2sqrt(2)/3)

wooden lily
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Thx Alot i love you. What math does a mf

viscid thistle
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Help. I'm stuck converting the trig function into exact form.
I've derived the function to -cos(5pi/6)
I have checked the marking guides and it is equal to root/2
What's the process for getting from the function to the esact value/ratio?

viscid thistle
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So I finally figured that bit out but now I have to put it into the gradient formula y-y1=m(x-x1)

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I did similar except instead of using pi/6, I made it 1/2 exact ratio since sin pi/6 exact ratio is 1/2, or am I not supposed to do that and leave it as pi/6 because you can't convert it as it is a point and not part of the sin function?
(Also I'm most farmiliar with slope intercept form over general form so that makes working backwards that little bit harder)

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Also I see questions happening in both places. In future is it better to just go straight to a "help" room?

viscid thistle
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<@&286206848099549185>

spare cobalt
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wrong channel

viscid thistle
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Hi

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So the question is Given f(x^2)=f(x)+x^2 find f'(1)

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I don't want the answer

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but a hint

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I'm stuck

tight compass
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Take the derivative of both sides.

river jasper
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Dont if you put x=1 you get 1=0?

tight compass
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Using the chain rule and try to express f'(1).

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@viscid thistle

viscid thistle
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yo

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Ight cheers

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i'll try that

river jasper
tight compass
river jasper
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In f(x^2)=f(x)+x^2

tight compass
river jasper
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If you put x=1 in that you get f(1)=f(1)+1

viscid thistle
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i got an answer

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one sec

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nah nvm im totally wrong