#help-17

1 messages · Page 164 of 1

lyric fossil
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you should give it a shot

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do not integrate by parts

sinful nacelle
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oo why? i just glimpsed over it

fluid pumice
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based off the syllabus, ibp isn't a thing

sinful nacelle
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ah

lyric fossil
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because it is overkill and you can do this directly from part i

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dan note that sin^2 = 1 - cos^2

fluid pumice
fluid pumice
lyric fossil
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and 1 - cos^2 = (1 + cos)(1 - cos)

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sub in and simplify

fluid pumice
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2(1 - cosx)/(1 + cosx)(1-cosx)?

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(2 - 2cosx)/(sin^2x) comes afterward

lyric fossil
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hold on

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what happened

fluid pumice
#

but then

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i get 1 - cosx as the numerator not 1 + cosx

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this was the main issue

lyric fossil
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[\int\frac{1 +\cos x}{\sin^2x},\dd x= \int \frac{1 + \cos x}{(1+\cos x)(1-\cos x)},\dd x]

twin meteorBOT
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maximo¹

glossy maple
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I suggest just subbing in y = sin(x)/(1 + cos(x)) instead

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u-substitution

fluid pumice
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okay so basically from the syllabus's generic solutions for any hence find this integral question

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you use the derivative you find from (i) and equate that to the original y + C

glossy maple
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??

lyric fossil
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wait dan do you know the integral of tan(x)sec(x)?

glossy maple
#

You are using the first part to find dx

fluid pumice
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but it's secx + C

ancient horizon
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wait nvm

lyric fossil
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ok never mind what i said, redstone is right

fluid pumice
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does redstone's solution use the answer from (i)?

lyric fossil
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yes

fluid pumice
#

okay so i remove the 2 from the integral

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idk how to use texit so bear with me

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integral of 1/(1 + cosx) = sinx/(1 + cosx) + C

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uhh

sinful nacelle
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ok i had a sit down and did the question, i think the easiest route by far is to try to use something very similar to the original function to differentiate into 2/1-cosx

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if you want i can show you pieces of my solution?

fluid pumice
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sure

sinful nacelle
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do you want the whole solution or just a hint?

fluid pumice
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just a start

sinful nacelle
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this looks very similar to what we got in part i, can we try and construct a function that would work for this based on what we know?

fluid pumice
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very similar

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but i don't see how you continue from here given the denominator is different

sinful nacelle
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well work backwards, mess around with the minus signs a bit

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you know that the denominator was v^2 via the product rule, and that v ended up cancelling out right?

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so what could the new demoninator be based on that

fluid pumice
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1 - 2cosx + cos^2x

sinful nacelle
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however, due to the negative that cos gives when differentiation, you may want to make the numerator negative to account for that

sinful nacelle
fluid pumice
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(1 - cosx)^2..?

sinful nacelle
#

it's simpler when a fraction in this case

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mhm

fluid pumice
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looks like this so far

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without the negative sign oops

sinful nacelle
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no, dont change the intergal any further

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use part i to help, you know what the integral of 2/1+cosx is, so you can really just mess with the minus signs

sinful nacelle
fluid pumice
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2/(1 - cosx)^2?

sinful nacelle
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where did the sinx go?

fluid pumice
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2sinx/(1 + cosx) this was the original f(x)

sinful nacelle
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mhm

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but how would getting rid of sinx help

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if the only difference is the signs, why would u want to get rid of trig functions completely?

fluid pumice
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to make life simpler i guess

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okay so what's the follow-up after what we just did with the denominator

sinful nacelle
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but then the denominator wouldnt cancel like how it did on the first time via sin^2x + cos^2x

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do u want to see my full solution and then ask any questions if u have any?

fluid pumice
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sure

sinful nacelle
fluid pumice
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but how do we integrate that

sinful nacelle
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so you already have the answer

fluid pumice
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so the answer is 1/(cosx - 1)?

sinful nacelle
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no, the answer is -2sinx/1-cosx ....

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we differentiated it to 2/1-cosx, yes

fluid pumice
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we divided it by 2

sinful nacelle
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and differentiating is the exact opposite of integrating

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oh yes sorry

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so -sinx/1-cosx

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remove a linear factor

fluid pumice
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and took out a negative sign?

sinful nacelle
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no?

fluid pumice
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we ended up with -(1 + cosx)/(sin^2x)

sinful nacelle
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but you already have the integral of 2/1-cosx

fluid pumice
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okay say that we have this expression that we constructed

sinful nacelle
fluid pumice
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how does it use any answer from (i)?

sinful nacelle
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becasue we used part i to be able to deduce how to construct this function

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its just 2 sign changes from part i

fluid pumice
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it's always the syllabus that restricts this from happening

sinful nacelle
fluid pumice
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but yes i would say it works

sinful nacelle
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i didnt use any non elementary methods

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i mean, idk ur syllabus but this is usually how hence questions are solved

fluid pumice
#

thanks though

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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vast shale
#

what

vocal sleetBOT
vast shale
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how do you go about doing this

lime gorge
#

Do you know what critical points are

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or using differentiation

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@vast shale ?

alpine night
# vast shale

Differentiate using the chain rule, put it equal to 0

viral copper
#

you can really use chain rule here directly

twin meteorBOT
#

²⁰Ne

viral copper
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now you can

vast shale
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that is what i thought

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times 3 right?

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so

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the derivative of e^x is e^x

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so

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the derivative of that whole thing

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e^xln(2x) * (d/dx(xln(2x))

lime gorge
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yea

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times 3

vast shale
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so

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3 (e^ln(2x)x * (x/2x + ln(2x)))

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right?

lime gorge
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ye

vast shale
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simplify x/2x to 1/2

lime gorge
vast shale
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that seems kinda stupid

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divide both sides by 3 and the 3 goes away

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then divide both sides by e^ln2x(x) and that goes away?

lime gorge
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cant just do that

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u have to set each factor equal to 0

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and solve

vast shale
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so the first factor is 3

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so 3 = 0? wtf

lime gorge
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yep, thats not true, so its not a solution

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but we just divided that by both sides

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i was more referring to non-constant factors

vast shale
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is 3 a critical point?

lime gorge
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so e^(x(ln(2x))) = 0 and (0.5 + ln(2x)) = 0

lime gorge
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we wanna find where x is 0

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if i multiplied both sides by 6, would 6 be a critical point? No

vast shale
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how the heck do you even solve for 0 with something as complicated as that

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log both sides?

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extract power?

lime gorge
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well think about it logically

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is there any number out there such that e^number = 0?

vast shale
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uh

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1?

lime gorge
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Whats e^1 equal to

vast shale
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e

lime gorge
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right, so that cant be it

vast shale
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e^0 == 1

lime gorge
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thats correct

vast shale
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so what the heck there is nothin

lime gorge
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Correct

vast shale
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ahh

lime gorge
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So we just eliminate that completely and move on

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now 0.5 + ln(2x) = 0

vast shale
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other one subtract 1/2

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and then..

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move 2 outside?

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ln(2) + ln(x)

lime gorge
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keep going

vast shale
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uh

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i have to have exact answers

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soo

lime gorge
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ok well u havent solved for x yet

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u have ln2 + lnx = -1/2

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keep going

vast shale
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subtract ln2 from both sides?

lime gorge
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keep going

vast shale
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then go

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e = x^(-1/2 - ln2)

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right?

lime gorge
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e = x^(something)?

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we are solve for x

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not e

vast shale
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you do that then you can go

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(-1/2-ln2) root of e

lime gorge
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u need to backtrack

vast shale
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im lost

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hints?

lime gorge
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So u got lnx = -0.5 - ln2

vast shale
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right

lime gorge
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now lets do this

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lets make a new variable b

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b = -0.5 - ln2

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so now we get ln(x) = b

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how do we solve for x

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what must we do to both sides

vast shale
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inverse ln?

lime gorge
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Which is?

vast shale
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e^x?

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no

lime gorge
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yes, we do e^both sides

vast shale
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e^b = x

lime gorge
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yes thats what it comes to

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e^(ln x) = x

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and then e^b is just e^b

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so x = e^b

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and whats our value of b?

vast shale
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lnx?

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so e^lnx?

lime gorge
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what

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ok i think i may have lost u

lime gorge
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look at th expoentital and logaritjmic property

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lnx = -0.5 - ln2

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what do we do to both sides

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to get ‘x’ by itself

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we just did it

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just asking u to repeat

vast shale
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so

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e^ln(x) = -1/2 - ln(2)

lime gorge
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no

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remember

vast shale
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(╯°□°)╯︵ ┻━┻

lime gorge
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whatever we do to one side, we must do to the other side too

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cant just do something on one side only

vast shale
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but its equivalent

lime gorge
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nope

vast shale
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right?

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it says right there

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x = e^ln(x)

lime gorge
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Thats showing that e^ is the functional inverse of lnx

lime gorge
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ur on the right track, just try again

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lnx = -0.5 - ln2

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whatever u did to the left side, do it to the right side too

vast shale
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e^ln(x) = e^(-1/2 - ln(2))

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what?

lime gorge
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correct

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there u go

vast shale
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how does that help though

lime gorge
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now what is e^(ln(x)) equal to

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simplify that

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using the exponential logarithmoc property

vast shale
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but wont i have to do it to both sides again?

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I'm confused

lime gorge
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Ur just simplifying, ur not doing e^ both sides again

vast shale
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how can you simplify this?

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e^ln(x) = -1/2 -ln(2)

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ln(x) = -1/2-ln(2)

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like that?

lime gorge
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Nope thats wrong

lime gorge
lime gorge
#

$a^{\log_a(b)} = b$

vast shale
#

why don't you need ln on the right side

twin meteorBOT
#

Stephen

lime gorge
#

i think ur issue is understanding how the functional inverse works

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e^ln(x) = e^(-1/2 - ln(2))

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when u get here, youve already done e^ both sides

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correct?

vast shale
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ah i see

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yeah

lime gorge
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after that e^ln just cancels out

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and it just becomes x

vast shale
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what about the -1/2

lime gorge
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what about it

vast shale
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so

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x=2?

lime gorge
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wha

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no dont change the right side up yet

vast shale
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so

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x=e^(-1/2-ln(2))

lime gorge
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yes

vast shale
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AHHH

lime gorge
#

This is a critical point

vast shale
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wtf

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weird

lime gorge
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we can simplify it down a bit

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using exponent properties

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see anything u can use?

vast shale
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negative exponent and fractional exponent

lime gorge
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ok yes we can use those, but first we must use quotient rule

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look at the a^{x-y}

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see how its just like our e^(-0.5-ln2)?

vast shale
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1/(\sqrt(e)e^ln(2))

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right?

lime gorge
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yes

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now simplify that

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e^ln2

vast shale
#

these little images with math stuff super helpful

lime gorge
#

fr

vast shale
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so its just 2

lime gorge
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Yep

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so we end up with?

vast shale
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1/(2\sqrt(e))

lime gorge
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Yes

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1/2sqrte

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so now thats our critical point

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but we have to do a few things now

vast shale
#

solve for maxima

lime gorge
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we need all extrema, not just maxima

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But first, check if 1/2sqrte is on our interval

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otherwise, its invalid

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and we cant use it for extremaa

vast shale
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it is

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.3032653299

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so plug it in?

lime gorge
#

But hold on, we arent done yet

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evaluate that into the calculator

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and see what u get

vast shale
#

4.178361968

lime gorge
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ok, now

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look at our interval

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is it including endpoints?

vast shale
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ye

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so plug those in

lime gorge
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thus

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Correct

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what do u get from those

vast shale
#

1 gives 6

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.1 gives 4.178361968

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i mean

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4.7649

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so .1 is maximum?

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1 is minimum?

lime gorge
#

u sure .1 gives that?

vast shale
#

nah 2.55401

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so its my weird value

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that is max

lime gorge
#

is this correct?

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check that again

vast shale
#

2.577911626

lime gorge
#

lol

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what happened

vast shale
#

idk

lime gorge
#

xd

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anyways

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what are the extreme max and mins

vast shale
#

hard to type this in calculator

lime gorge
#

ye i gotchu

vast shale
#

max is 6 at 1

lime gorge
#

and min?

vast shale
#

uh

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2.554019768 at .1

lime gorge
#

yep

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so in the end

vast shale
#

but needs to be exact

lime gorge
#

We didnt end up using the critical point happy

lime gorge
#

just do the plugged in version like u showed before

vast shale
#

this is wrong

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oh crap .1

lime gorge
#

Lol

vast shale
#

so if i replace x = with .1 its right?

lime gorge
#

well ehats the question asking for

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Max or min

vast shale
#

nope it says this

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wtf is that

lime gorge
#

what is that for

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max or min

vast shale
#

that isn't even the critical point we found

lime gorge
#

lets see

vast shale
#

i feel better now that someone way smarter than me also is confused

lime gorge
#

well lets see

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im p sure thats the same answer lol

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hold on

#

$3(2(\frac 1{2\sqrt e}))^{\frac 1{2\sqrt e}} = 3(\frac 1{\sqrt e})^{\frac 1{2\sqrt e}} = 3(\sqrt {\frac 1e})^{\frac 1{2\sqrt e}}$

twin meteorBOT
#

Stephen

vast shale
#

what the heck

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gotta do it all over again

lime gorge
#

yea hold on im still trying to understand

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bear with me ive only a phone keyboard lol

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im on discord web version on phone

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i see exactly where we went wrong

lime gorge
#

shoulda caught this earlier on

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try that part again

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thats crazy bro

vast shale
#

the question is different now

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anways lets solve the original one

lime gorge
#

Well at least ya learned something

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good job for persisting

vast shale
#

i can solve it now on my own i think

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but what is wrong with how I did it?

lime gorge
#

many people just quit

vast shale
#

i dont see

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is the x/2x wrong?

lime gorge
#

yes

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we need chain rule on the 2x

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so it becomes x/2x * 2

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which is just 1

vast shale
#

ahh

lime gorge
#

man i wish i caught that

vast shale
#

yeah that makes it a lot easier

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i think i can solve the new one on my own

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let me try

lime gorge
#

sure, lmk if u need help

vast shale
#

so its

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1/(2\sqrt(e))

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thats the other critical point

lime gorge
#

Is that ur new problem

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ok lets see

vast shale
#

its wrong

lime gorge
#

do u have a new problem now

vast shale
#

factors i got are

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2

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e^xln(2x)

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(1+ 2ln(2x))

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its almost exactly the same as before

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solving for 1+2ln(2x) = 0 gives me

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x = 1/2\sqrt(e)

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sorry if thats hard to read

lime gorge
#

I didnt get that

vast shale
#

where did i mess up

lime gorge
vast shale
#

why no 2 in front of the ln?

lime gorge
#

on which line

vast shale
#

3rd

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isn't that chain rule so it goes outside

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oh

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that's what i did

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so ts just 1/2e

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same mistake i made before

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😄

#

thanks so much

#

.solve

#

.solved

vocal sleetBOT
#
Channel closed

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Use .reopen if this was a mistake.

lime gorge
#

Have a good one bro

#

keep working at it

#

u have good perseverance

vocal sleetBOT
#
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noble umbra
#

Sorry my last help channel dissappeared can someone help with my data man assignment, thanks!

vocal sleetBOT
#

Please don't occupy multiple help channels.

noble umbra
#

a quick check over to see if everything looks good would be appreciated

#

<@&286206848099549185>

vocal sleetBOT
#

@noble umbra Has your question been resolved?

vocal sleetBOT
#

@noble umbra Has your question been resolved?

vocal sleetBOT
#

@noble umbra Has your question been resolved?

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#
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carmine mesa
#

Can someone explain to me how the answer is B

heavy yoke
#

which one do you think it should be?

carmine mesa
#

I know the answer is B. I just hope someone can explain this to me because this is the only thing on the study guide I don't know how to solve and I don't really know how to do these "Areas in Polar Coordinates" things from out of everything in the unit

#

wait okay now I see why

#

but can you explain why it's B and not D? @heavy yoke

heavy yoke
#

you want to pick the right bounds so that the curve goes all the way back to where it started

carmine mesa
#

AHHHHHHHHH I see

#

and if we picked D, it would've been half of that

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right?

heavy yoke
#

in this case it would integrate only half of the curve, yes

carmine mesa
#

gotcha

#

thank you so much

#

.done

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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Ask your math question in a clear, concise manner.
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prime cradle
#

help meee, somebody helpppp

vocal sleetBOT
prime cradle
#

if i was required to learn this topic in less than an hour

tidal dock
vocal sleetBOT
# prime cradle
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
prime cradle
#

I have a general idea

#

I thought I had the topic but when I checked my work I found out I was wrong

tidal dock
#

show your work

prime cradle
#

I just assumed from the way it looked

tidal dock
# prime cradle

can you identify the equation of this line? without the shaded area, just the line at the boundary?

tidal dock
#

do you know what is the equation of the blue line, roughly?

#

replace all $\geq$ and $\leq$ in your options with $=$ and you get two equations of lines

twin meteorBOT
#

artemetra

tidal dock
#

one of them will be the blue line

prime cradle
#

oh

#

I'll try that

#

thank you

#

y=4x+3

tidal dock
#

yep

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so first two options are out

prime cradle
#

I'd say y is less than or equal to

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wait no greater than or equal to

tidal dock
#

correct

prime cradle
#

o

tidal dock
#

no

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less then

prime cradle
#

can you explain why

#

I thought because it went to the right

tidal dock
#

why? think about it like this: the shaded area includes all values of y for which it is smaller or equal to 4x+3

prime cradle
#

OH

#

that makes so much sense

#

thank you

tidal dock
#

any other question?

prime cradle
#

I don't think so

#

thanks for all your help

tidal dock
#

no problem, if you are done, type ".close"

prime cradle
#

.close

vocal sleetBOT
#
Channel closed

Closed by @prime cradle

Use .reopen if this was a mistake.

vocal sleetBOT
#
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brittle shell
vocal sleetBOT
brittle shell
#

Been stuck on this question

subtle blaze
#

What have you tried so far?

brittle shell
#

Um using 6 as the hypotenuse and then doing a2+b2=c2

#

I dont know where im supposed to start because Im only given height and a base and a hypotenuse

#

The formula is SA=Ph+2B

#

I got 4.8 but now I have no idea what to do with it

mild flower
#

surface area is just a matter of finding all of the areas of the shapes and adding them up

#

in this case we have two triangles (front, back) and three rectangles (bottom, left, top)

#

what did you get 4.8 for?

brittle shell
#

A2+b2=c2

#

C=36
B=12.96

#

Then I got 23.04 from subtracting them

mild flower
#

okay, so a = 4.8; what does that mean on your image? can you label the side that is 4.8 (unit??) long?

brittle shell
#

Then I square rooted it to get 4.8

brittle shell
mental falcon
mild flower
#

(that's not the right edge...)

brittle shell
#

Ohhhhh…

mild flower
#

that one you already know how long it is

#

the pythagorean theorem applies to right triangles. can you label a right triangle in that image? color it in green for me.

brittle shell
mild flower
#

those are right angles

#

which is a good start

#

but we want a right triangle

#

which is a 2d shape

brittle shell
mild flower
#

yes good

#

now, do you know the lengths of any of the sides of that triangle?

brittle shell
#

Um 4.8 sorry im bad at labeling

mild flower
#

which side is 4.8?

#

feel free to use more colors to make yourself clear

brittle shell
mild flower
#

that's not even part of the triangle!

#

didn't you use the pythagorean theorem to calculate 4.8 inches?

brittle shell
#

Yes

mild flower
#

the pythagorean theorem applies to right triangles

#

considering your right triangle that you've labeled -- the green one -- which side lengths do you know?

#

one of them is labeled already

brittle shell
#

3.6

mild flower
#

which side is 3.6?

brittle shell
mild flower
#

okay, you could have said "the blue one" but that works

#

are there any other side lengths in that triangle that you know?

brittle shell
#

I dont think so maybe 6 but what would be for the other triangle

mild flower
#

the two triangles are going to be the same

#

since this is a prism

brittle shell
#

Ohhh

brittle shell
mild flower
#

so knowing this, are there any other side lengths in that triangle that you know?

#

okay, using your words, which side lengths do you know in that triangle?

brittle shell
#

3.6

mild flower
#

using your words

#

"the purple side is 7.8 inches long"

#

is what your answer should look like

#

but with different colors and numbers

brittle shell
#

How did you get 7.8?

mild flower
#

i didn't

#

there's also no purple side

#

this is an example answer, to show you the format that i'd like you to answer in

brittle shell
#

The purple side is 3.6in

mild flower
#

(that's blue but ok sure)

#

any others?

brittle shell
#

And another 3.6 because they are the same?

mild flower
#

which other is 3.6?

brittle shell
#

We are given 8.5 but that would be the height?

mild flower
#

okay, i think that black number you've written is referring to the vertical line in the back? that's great, but what we care about is the triangle in front

#

you very excitedly circled the "6 in" in the back -- why?

brittle shell
#

Because you said that it would be to same for the other triangle since

#

But I thought that 6 was the hypotenuse and not a side

mild flower
#

the hypotenuse is also a side

brittle shell
#

Ohhhh

mild flower
#

it's not a leg but it's a side

brittle shell
#

I got taught that in what ever direction the square is facing that would be the hypotenuse for the problem

mild flower
#

well, yes, the side opposite the right angle is the hypotenuse

brittle shell
#

So 6 would be another side then

mild flower
#

yes... one of the sides of the front triangle is 6 inches long

#

which side?

#

blue, orange, or green?

brittle shell
#

Orange

mild flower
#

okay. so which side lengths do you know, in that front triangle?

#

the blue-orange-green one

brittle shell
#

6 and 3.6

mild flower
#

the blue side is ___ long
the orange side is ___ long
the green side is ___ long

#

please fill this out

#

or put in ??? if you don't know

brittle shell
#

the blue side is 3.6 long
the orange side is 6 long
the green side is ? long

mild flower
#

okay cool

#

now can you use that information to find the length of the green side?

brittle shell
#

Would I use the Pythagorean theorem?

mild flower
#

perhaps

#

the pythagorean theorem is for right triangles

#

do you have a right triangle?

brittle shell
#

So I would do 6squared which is 36 then

#

3.6 squared to get 12.96

mild flower
#

okay, keep going...

brittle shell
#

Then add both to get 48.96

mild flower
#

i don't think you want to do that

brittle shell
#

Subtract

#

Subtract 36-12.96

mild flower
#

,calc 36 - 12.96

twin meteorBOT
#

Result:

23.04
brittle shell
#

Which is 23.04

#

Then square root it to get 4.8

#

So circumstance = 4.8

mild flower
#

circumstance?

brittle shell
#

Base?

mild flower
#

shrug

#

which side is 4.8?

brittle shell
#

So I would add 4.8+6+3.6 to get 14.4

mild flower
#

uh

#

why

#

also

#

you didn't answer my question

#

which side is 4.8?

brittle shell
#

And then height =8.5

mild flower
#

meyvis

brittle shell
#

Yes

mild flower
#

i don't know which side that is

brittle shell
mild flower
#

okay yes good

#

here

#

what is the length of each color? you should label them on your piece of paper

brittle shell
#

Blue =3.6
Orange =6
Green=4.8

mild flower
#

okay, and yellow?

brittle shell
#

Yellow is 8.5

mild flower
#

now do you have enough information to compute the area of each side?

#

at this point i'd like you to start keeping track of your units

#

blue = 3.6 inches
orange = 6 inches
green = 4.8 inches
yellow = 8.5 inches

brittle shell
#

Ok gotcha

mild flower
#

keeping track of your units will make sure that you don't make an error

brittle shell
#

The equation for problem is SA=Ph+2B

mild flower
#

i don't know what any of those variables mean

brittle shell
#

Now im assuming that I would be adding 3.6+6+4.8 to get 14.4

#

P stands for perimeter and h stands for height and B is base

mild flower
#

okay... sure that seems fine to me

brittle shell
#

Thats the equation I received

mild flower
brittle shell
#

Inches

mild flower
#

okay

brittle shell
#

So I would do B=1/2(3.6)(6)

#

To get 10.8

mild flower
#

screams units

brittle shell
#

Inches

mild flower
#

redo it

#

with units

#

B = ?

brittle shell
#

B=10.8 units

mild flower
#

no that's not at all what i meant

#

B = what

brittle shell
#

Huh???

#

B = base

mild flower
#

you have something like B = 1/2 b h right?

brittle shell
#

Yes

mild flower
#

okay

#

what is b?

#

what is h?

brittle shell
#

B=3.6

#

H=6

mild flower
#

you've made a distinction between B and b

#

so please keep it that way

#

but also

#

UNITSS

#

b = 3.6 what

#

3.6 jellybeans??

brittle shell
#

3.6 inches

mild flower
#

we're trying to find the area of this triangle, right?

brittle shell
#

Yes

mild flower
#

what are b and h?

#

base and height?

brittle shell
#

base is the green part right?

mild flower
#

yes

brittle shell
#

4.8

#

Ohhhh I see now

mild flower
#

stop giving me numbers without corresponding units

#

they mean nothing

#

you can use "in" for inches

brittle shell
#

4.8in

mild flower
#

okay

#

so what is the area of this triangle?

brittle shell
#

Just making sure h=6in because we are solving for a right triangle

mild flower
#

which side is 6in?

brittle shell
#

Orange

mild flower
#

that is not the height of the triangle

#

the height of the triangle is perpendicular to the base

#

do you know why the area of a triangle is 1/2 b h?

brittle shell
#

Wait no sorry 8.5in

mild flower
#

it's because it's half of a rectangle

mild flower
brittle shell
#

Wait no then blue would be the height

mild flower
#

yes

brittle shell
#

B=1/2(4.8in)(3.6in)

mild flower
#

cough

#

i see numbers

#

without units

#

great

#

now what is B?

brittle shell
#

B=8.64

mild flower
#

that's a number

#

without a unit

brittle shell
#

B=8.64in

mild flower
#

you can calculate the unit

#

notice

#

that you are multiplying in times in

#

which will not produce in

#

but rather in²

#

which is a fundamentally different unit than in, since in² measures area and in measures length

brittle shell
#

Wait so is my answer right for Base im confused?

mild flower
#

what's Base supposed to be?

brittle shell
#

8.64in

mild flower
#

that's a measurement of length

#

what's Base supposed to be? like, use your words

brittle shell
#

I got 8.64 by multiply 4.8 x 3.6 then halfing it

#

To get 8.64in for Base

mild flower
#

the next time you give me numbers without units i'm leaving for 10 minutes

#

you multiplied 4.8 in x 3.6 in

#

,calc 4.8 * 3.6

twin meteorBOT
#

Result:

17.28
mild flower
#

which would give you 17.28 in²

brittle shell
mild flower
#

do you see the little 2 up there?

brittle shell
#

Yes

mild flower
#

in² is also called square inches

brittle shell
#

Ohhhh

mild flower
#

it's a unit of area

#

and yes we'll still need to multiply by 1/2

brittle shell
#

Ohhhh so thats what you we’re talking about

mild flower
#

you can also write sq in if writing ² is hard

brittle shell
#

B=8.65sq

mild flower
#

great ok

#

so

brittle shell
#

Alright good good

mild flower
#

where are we, let's go back to the formula you had for surface area

#

SA = Ph + 2B

brittle shell
#

Yes

#

Perimeter you would add all parts

mild flower
#

yes, you found P earlier

brittle shell
#

3.6in+6in+4.8in= 14.4in

mild flower
#

good

brittle shell
#

Ok ok great

mild flower
#

and what's h? i think you got confused earlier because this should be the height (really the length in this case) of the prism, not the height of the triangle

brittle shell
#

Wait would it be 8.5in?

mild flower
#

yep

brittle shell
#

Ok great

mild flower
#

and you know B = 8.65 in²

brittle shell
#

Yes

mild flower
#

so can you use all of that to find SA?

brittle shell
#

SA=14.4in(8.5sq)+2(14.4in)

mild flower
#

i think you substituted in the wrong spots

#

are you using pencil and paper at all to keep track of what's going on here?

#

i hope you're not constantly scrolling through the chat

brittle shell
#

Im just keeping it in my head 🫠

mild flower
#

don't do that

brittle shell
#

But I understand where I got

mild flower
#

short pencil > long memory

#

i usually just keep a stack of printer paper near me to doodle whatever

brittle shell
#

Ok ill do that

mild flower
#

anyway yes you seem to have substituted incorrectly, in particular i see two copies of "14.4 in"

#

which i don't think should be the case

brittle shell
#

Oh wait was that supposed to be 8.5sq

#

SA=14.4in(8.5sq)+2(8.64sq)

mild flower
#

you're having so much trouble keeping track of these things

brittle shell
#

Im going to just say them
P=14.4in
h=8.5in
B=8.64sq

mild flower
#

good

brittle shell
#

SA=Ph+2B

#

So SA=14.4in(8.5in)+2(8.64sq)

mild flower
#

where did 8.5 sq in come from?

brittle shell
#

Height

mild flower
#

ah you corrected it

#

ok

#

now you can continue to calculate

brittle shell
#

So then the final answer would be 139.68sq

#

SA=139.68sq

mild flower
#

note that you can add inches and inches, and you can add in² and in² together, but if you ended up in a situation where you had like 4in + 7.3sq then you'd know something went wrong

brittle shell
#

Alright well I submitted the answer and it was correct 👍

mild flower
#

right

#

in the future, use paper! or a whiteboard or something

brittle shell
#

Thank you for your time I really appreciate it!

mild flower
#

just write stuff down

brittle shell
mild flower
#

no one's going to look at it but it can help you keep track and figure out what went wrong

brittle shell
#

Ok thankyou

#

How do I close this?

mild flower
#

type .close

brittle shell
#

Ok alright thank you again

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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weary gale
vocal sleetBOT
weary gale
#

Kind of confused on this

#

i think she messed up on step 2

#

since if it was perpendicular wouldnt it be opposite reciprocals ?

lone linden
#

yeah

weary gale
#

like

#

the wrong slope with the right slope

#

and redo the equation with the correct slope this time

lone linden
#

yeah

weary gale
lone linden
#

where's the x

weary gale
#

oops

#

so y = -2/4x - 4 ?

lone linden
#

you can't just copy the incorrect y intercept over

#

also -2/4 can be simplified to -1/2

weary gale
#

i forgot to simplify

#

mb

#

wouldnt we have to change the -4 to a + 4 ?

#

since its a negative now

lone linden
#

just use point slope form...

#

$y-(-2)=-\frac{1}{2}(x-4)$

twin meteorBOT
#

Civil Service Pigeon

lone linden
#

I gotta dip but you should get ||y = -x/2||

weary gale
#

i struggle with that

#

alright

#

thanks for the help

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

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opaque trench
#

how do I figure out how to make -2 rad be in the domain 0 and 2pi

opaque trench
#

,tex for z conjugate it would be $8\cos(2)-i8\sin(2)$

twin meteorBOT
opaque trench
#

but then you can make the angle -2

#

,tex $8\cos(-2)+i8\sin(-2)$

twin meteorBOT
opaque trench
#

I feel like I just can't visualize where -2 on the unit circle is and to try to find the angle on right domain

crystal gazelle
#

How many radians are there in a circle?

opaque trench
#

2pi?

crystal gazelle
#

Indeed

#

So

#

If you travel a full revolution of a circle to the point where you started

#

You've travelled 2pi rads

opaque trench
#

yes

crystal gazelle
#

So if you add any integer multiple of 2pi to the argument, it produces the same angle

opaque trench
#

ohhhh

#

so 2pi - 2

#

?

crystal gazelle
#

Exactly

opaque trench
#

thanks i don't think i could've thought that way

crystal gazelle
#

Np!

opaque trench
#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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livid oxide
vocal sleetBOT
livid oxide
twin meteorBOT
#

nox💫

livid oxide
#

what

#

they all have x-1

#

so that narrows it down to 1st and second one

#

correct?

#

so confused

#

so which one would it be

#

like how do i find out

#

mane

#

can you show@me how to do it

vocal sleetBOT
#

@livid oxide Has your question been resolved?

livid oxide
#

how would i get the residual for 4 hours

vocal sleetBOT
#

@livid oxide Has your question been resolved?

vocal sleetBOT
#
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vocal sleetBOT
#
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vast shale
vocal sleetBOT
vast shale
#

How should I approach this type of questions?

#

Is there something like f(0)×f(1)<0, saw it in answer can't really understand

#

Or maybe another way to approach this question

bronze osprey
# vast shale

It's a quadratic so there can be maximum two roots

vast shale
#

Yes

bronze osprey
#

So check the sign of that function when x = 0 and x = 1

#

If you get positive, positive or negative, negative

#

There must be a turning point in between, or the function was simply positive/negative all the time there

#

So if you get positive, negative or negative, positive

#

This implies there is exactly one root in [0, 1)

#

Oh you also have to check if x = 0 is a root cause of the closed bracket

vast shale
#

Ok

#

I will try

bronze osprey
#

No worries

vast shale
#

thanks @bronze osprey

#

.close

vocal sleetBOT
#
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bronze osprey
#

No worries!

vocal sleetBOT
#
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coral glen
vocal sleetBOT
coral glen
# coral glen

I understand that we are using the pigeonhole principle, however is it expecting us to write the answer in some sort of equation..?

edgy sapphire
#

nah you'd just write out a set and apply the principle

twin citrus
edgy sapphire
#

like the blueprint for these proofs is: there's a set {a,b,c,d,...} of size n, and by pigeonhole if you pick n+1 from this set there's overlap

twin citrus
edgy sapphire
#

the set is {1,2,3,...9} for people to know

twin citrus
#

why not {1,2,3...10}

#

a to know

#

yes of course

#

then?

edgy sapphire
#

9 is max because that's how many other people there are

#

then 10>9 so pigeonhole and you're done

twin citrus
edgy sapphire
#

idk how to, pigeonhole is usually like a 1 step proof

#

each person has a number 1-9

twin citrus
#

like in terms of sets how would you describe this problem

edgy sapphire
#

I mean I said the set already

#

there's a set and it's smaller than the number of people

twin citrus
#

so how could you do that?

#

i am 5 years old

#

5,5 ok

#

so approximately 6

edgy sapphire
#

I subscribe to feynmann quotes instead sry

twin citrus
vocal sleetBOT
#

@coral glen Has your question been resolved?

vocal sleetBOT
#
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#
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solemn falcon
#

Hoping for help on this question because in class we haven’t looked at graphs yet nor intervals on integrals

flint idol
#

how do we usually look for global and absolute maxima?

solemn falcon
#

take a derivative?

flint idol
#

yep

#

so we need to find $\frac{d}{dx} \int_{0}^{x} f(x) dx$

twin meteorBOT
flint idol
#

are you familiar with the fundamental theorem of calculus?

solemn falcon
#

not overly derivatives were my weakness and we just moved to integrals

flint idol
#

so basically the fundamental theorem states that:

$\frac{d}{dt}\int_{0}^{t} f(x) dx=f(t)$

#

!occupied

vocal sleetBOT
#

Someone else is already using this help channel. If you need help with a question, please open your own help channel/thread (see #❓how-to-get-help for instructions).

solemn falcon
#

I have seen that formula before

twin meteorBOT
flint idol
#

yep

#

we need to use this to find the derivative

#

so all we really have to do is plug in that t for x

#

and in our case, we’re just going to replace the t in f(x) with x

#

and that’ll be our F’(x)

solemn falcon
#

an x at the top of the integral sign?

#

where the t is?

flint idol
#

so basically i’m trying to say $\frac{d}{dx} \int_{0}^{x} f(t)dt=f(x)$

twin meteorBOT
flint idol
#

by the fundamental theorem of calc

solemn falcon
#

okay okay

flint idol
#

so yeah basically replace the t with the x

#

and to find our critical points we usually set our derivative equal to?

solemn falcon
#

0

flint idol
#

yep

#

so what would be our critical points

solemn falcon
#

0

#

?

flint idol
#

yep that’s one

#

there’s a few more

solemn falcon
#

but theres no numbers just variables?

flint idol
#

if we set $F’(x)=f(x)=0$

twin meteorBOT
flint idol
#

what value of x gives us 0?

#

the graph f(x) is given to us

#

basically look for the x intercepts of the graph

solemn falcon
#

-6,4?

flint idol
#

-6, 4, 0

#

and one more

#

we need to include the endpoints

solemn falcon
#

6

flint idol
#

yep

#

and now we have to observe how the sign changes around that point

#

so let’s start at -6

#

how does the sign change near that point?

solemn falcon
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-6 is up

flint idol
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what do you mean by up?

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increasing near -6?

solemn falcon
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yes sorry

flint idol
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yeah alright

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so basically for endpoints

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we just need to look at the right or the left of the endpoint

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if F’(x) is positive to the right that means that at x=-6, there is a?

solemn falcon
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positive?

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inf?

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sorry brains at all time low rn lol

flint idol
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i meant to ask if it was a relative min or max

flint idol
solemn falcon
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min

flint idol
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yep that’s correct