#precalculus
1 messages · Page 21 of 1
why not?
can't one do that with limits already?
yes you can
Not sure what you mean by this
ok
if you do the math you know that D(t) is continuous
so you could calcualte D(10) through limits
but its far easier to just plug in the 10 directly
what do you mean by continous
like its graph doesnt break
it isnt any sudden jump
or gets weird shapes
that make the existence of limit impossible
yeah for this one it is continuous
mhm
so you can just calculate D(t) generally
put it as a formula
and put 10 in the formula
are you trying to set up the derivative there?
it should be something more like
that's what i did, no?
lim h(10+Δ)-h(10)
Δ->0 ----------------- = D(10)
Δ
so delta t reaches 0?
i tried that, but It didn't work
alright
i just gave up at the end
lol
also I know i put the fractions as numbers
but whatever
hey guys is this question correct?
Yes
thanks
np
this isnt precalculus but can you also check this one please 💀
im thinking its d
not sure
x is linear, x squared is like the on you sent, and x cube is like a zig zag lookin
yeah
blud, you taking class in logic?
but i thought B was the answer first
i got an ACT exam tmrw morning 💀
wait, b and c both sound correct
👽 hi guys
i just tried 2 x's
sup
oh.
you're taking class in philosophy?
?
nah but idk most of the times questions like these come
wait why cant i send photo
you just have to substitute x and try to see if you get the same position
im doing ACT international subjects
where did i blunder
what is that
alright let me write it here
and im doing M1 for the 3rd time tmrw lmao
-1/30(t+Δt)^3 is part of h(t+Δt) right
exams that i need to do so i can get an american high school diploma
d is correct
right
i saw that you wrote it as -1/30 (t^3 + (Δt)^3)
maybe im wrong
but thats what i saw
that's what i wrote it as
yeah thats wrong
hold on, did i?
idk
even I'm confused
imma check again if you wrote it as that
thanks
yes, that's wrong?
hint: (a+b)^n usually isnt a^n + b^n
remember (a+b)^n indicates multiplication
it doesn't work for n = 2
so (a+b)(a+b) = a^2 +2ab + b^2
i will NEVER become a mathematician
(a+b)^3 = a^3 +3a^2b + 3ab^2 + b^3
of course, 10 must times delta t
I see
nah more like
10+ Δt must times itself
isn't that the same?
not really
do i explain with a cool visualization
or do you want to just use the formulas
if (a+b) ^n , doesn't that mean that (a+b) (a+b) (a+b)
i thought I had factorization in check, how the heck am I still missing
so must times with delta t, no?
and plus
i mean yeah but also gotta sum the 10
yes that
ok so
to clarify
(10 + delta T) ^3 means that 10 and delta t times each other three times and add
agree?
maybe you worded it wrong and thought it right
I said three times, but yeah
but this is how i would say it:
you get the idea
(10 + delta t) multiplied by itself 3 times
that sounds kind ambigious
alright wait
so you know how for a number a, a^2 represents the area of a square with each side length being a right?
like
each side length is a
and the area of blue square is a^2
are you getting it?
of course
alright so
yes yes, this I know
wait let me draw 2nd square
this square has side lengths a+b
so its area must be (a+b)^2
right?
so in total its a^2 +2ab + b^2
Hmm, I've heard that term but couldn't quite wrap my head around it
(a+b)(a+b) = (a+b)a + (a+b)b = a^2 +2ab + b^2
ohh
with distributive i mean distributive law
sorry if i overcomplicated this
no no, I was reffering to the law you meantioned
MMM
want to try again now?
yes
alright
tell me if you need help
you can dm
meanwhile imma go back to discussion
will do, thanks!
that is a devious lick
trying to get some help on this question, i need to find b and -b with lines passing through 12,0 and that are tangental to the circle at the origin with a radius of 6
sure! so this type of problem tests what you know about angles and triangles
now the first step in a problem like this is recognizing that the radius of 6 can be used to make a triangle between the origin, point P, and (12,0)
now since we know that the lines are tangent to the circle, we can establish some right angles
and so by doing that we would be able to recognize a solvable triangle here
so we're able to break this triangle out and solve for x using the pythagorean theorem since we know its a right triangle.
this gives us an $x$ value of $6\sqrt{3}$
architecture2
and so from there we can realize that by similar triangles we can find the other angles in this triangle
from there we can use what we know about angles to solve for this triangle here, which gives us the value of b
so by similar triangles we can see this
and then we can use the 60 degree angle to find that the angle between the y-axis and point P is 30 degrees, and we can go forward from there to find b using similar triangles again
ofc keeping in mind that this is the similar triangle we're using
ohhh i didn’t even think of making a triangle, even though i knew CP was perpendicular to (12,0)P lol
i’m assuming this works reguardless of where the point is because a tangental line will always make a right triangle with CP
thank you!
ofc
hey is there anyone which is at university level on math?
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question! See https://dontasktoask.com/
@tropic coyote Bro, I need help
I’m STILL!! Stuck at the same problem from yesterday 💀
hi
Hi
what happened
How tf did I even come to this conclusion!!!
alright what happened
send photo of work
I’m seriously contemplating life after the last bit
Of course I did
alright let me send photo
ok
$(a+b)^3=a^3+b^3+3a^2b+3ab^2$
You're welcome HSF
yeah except if it was a and b i was dealing with, I wouldn’t have an issue with visual spatial reasoning
I see just replace a with 10 and b with del t
I seriously have no idea where I went wrong
Your expansion is wrong
Hmm, how come
@tropic coyote How quick did you solve this problem?
i used another trick to find derivatives
not limits
so in some minutes
its a lot harder with limits
oh yeah i found an error
I can find others maybe but sorry I'm not doing well
Ok so How did It was first take (a +b) (a+b) then multiply that with (a+b)
yeah i got that part
You're using the first principle arent you?
but thats correct no?
If thats what its called, then sure
let me send photo of my own work
$10(\Delta t)^2 \neq (10\Delta t))^2$
I don’t know any other ways then using limits
well other than using tangent lines
the other tricks basically depend on limits
but screw that
You're basically in the process of learning it dw
It's not about speed it's about understanding
i dont know why it keeps getting rotated
im trying to do it like you did
so you can find error
,rccw
There
This is hard to read ngl
Wait
sorry if its blurry
I can't write cause I'm literally in bed but
ill send photo of next step
😂
I’m unaware, are there any other tricks than limits?
$$h(10+\Delta t)=-\frac1{30}(10+\Delta t)^3+\frac52(10+\Delta t)^2$$
Using limits is a tedious process
i mean there's some patterns in derivatives
like the power rule, chain rule, the fact that derivative is linear
etc
speaking of, that’s exactly what I’ll learn next
oh
I got the exact same result
,rccw
but i wrote 10 (delta T)^2 as (10 delta T) ^ 2
yeah thats the error i found
theyre different things
10Δt*10Δt = 100ΔtΔt
10Δt*Δt=10ΔtΔt
Did I do that?
you did the wrong version
Ugh, I probably have to redo this entire thing
it’s so easy to lose control over things
alright it should look like the last one
do i simplify to almost last step so you can revise your own work
or do you wanna do it yourself
I wanna do it myself
okay
so to clarify, I can do (a+b) (a+b) then multiply that with (a+b)
correct?
@tropic coyote
yes
binomial coefficients are easy to learn if you think of it as pascal's triangle
so I’m just doing it the old way
alright
Yes its easy to understand
but Goddamn is it tedious
and looooooong
Don't actually learn binomial expansions and do hard questions
wanna see a cool math trick?
actually no, it’s not so easy. Until you get to nCr ! etc then it gets complicated
Sure
alright let me use pc drawing for this
Wait why do I have med lol
it sounds like a riddle if you don’t even know what it means
Kinda... I always thought differently about it since my first combinations class in 2021
Idk before that I didn't care
there i ordered the first few binomial coefficients in a triangle
Yeah, pascals triangle
see any pattern there?
Yes
what is it
1’s are always outside and the middle ones add up
yes
look at it with more numbers
ive seen it, but thats not the issue
the problem is the nCr or whatever it means
nCr/ ncr !
or sum like that
are you a programmer by any means?
You doo?!
Yeah?
Ah shhhh
but do you code on python?
Yeah I code in manim
I’m kinda in need for some lectures in python with physics
cool word I guess
I gotta stop gobbling libretexts on my morning walks tbh
i should do it more
but yeah, physics + python
I have no idea how python works, even though i had some python lectures in my physics class
What’s desmos?
😫
I almost went insane💀
what
can’t lose my sanity over calculus
nothing, it’s just that calculus graphs give me ptsd
remind me of the hell I’m about to endure in the future
Duh
I remember looking at limits when I was first a math newbie
like when I was learning basic algebra
Well applied calculus is fun
and now I’m here doing them
That's the only thing I like in physics
Yeah but not so fun doing the math itself and losing your mind in the process 😭
anyways if you want to i can give you photo of next steps i did
there are more steps?
Uh what'd you do
yeah like 3 steps
i thought h’(t) was it
Did you put the limits?
yes
yeah the next step is factoring no?
then substituting t with 0 and using the remainders
You didn’t even factor first?
i mean you could
so when you divide you divide all the terms right?
yes
since it ain’t factored
ok
so it may be kind of confusing
oh alright
so you get left with the terms that were next to a single delta t
and those terms are
-(300)/30
- 5*(20)/2
hold on, you haven’t multiplied with -1/30, that’s what bugs me the most
i did though
Why is -1/30 standing outside the parentheses?
yes so… don’t u remove the term after multiplying
well i don’t know how you americans do it, but seems like we have our own methodology
its still another country
I know I was just joking
You couldn’t tell?
anyways do you want to do the factoring yourself now?
at last, I’ll try this dumb problem one last time
because it seems we have different ways of doing it
Yes
small details though
But wait, do you get -delta T/30 after multiplying delta T with -1/30?
yes
yeah
so far this is what I have, any mistakes? @tropic coyote
this is the (10 + t)^3
h(10) i got 650/3 or 216.66
if it’s wrong then just say it
Ok… moving on
@tropic coyote agree?
the sum of h(10) is 650/3
of what I got
hello?
@tropic coyote Are you alive?
Sorry If I’m bothering you
yeah i think thats right
Alright
theres a slight error there
you also substracted part of h(10+Δt)
because the 2nd 650/3
comes from the expansion of h(10+Δt)
What?
oh sorry
just continue like you were doing before
and ill tell you if theres an error
every step up to what you showed me is right though
Alright
so even if you get a step wrong now you wont have to start from scratch
now, i still have the multiplier-1/30
I’ll multiply it with all the terms
And this is what I’m left with
I feel like I’m doing a mistake here
@tropic coyote
back
let me check if the math works out
nah that parts wrong
sorry
Bruhhh😭🔫
ok where did I blunder?
idk can i see how you did h(10+Δt)-h(10)
why do a +650/3
h(10) was 650/3
💀
I always forget
summary
Ok tell me
yuh
so you got ((10+Δt)^3)/-30 + (5(10+Δt)^2)/2 - 650/3 right
yes
now you can pick the same terms in the expansions of both of the parts of h(10+Δt)
to get 650/3
so you get 650/3 -650/3
and youre left with only numbers that are multiples of Δt
only numbers that are multiples of T you say
nah Δt
Yeah
remember we already set t=10
you’re not using limits?
yeah im using limits
but im using Δt->0
sorry if we're using different variable names
when i say t im reffering to delta t
if t approaches 0, then how do you set T equal 10?
because with deltas, we’re expressing a change from t1 to t2
yeah
so in essence it would be like saying delta t approaches 0, because the number is, well 0
with comma
if im not mistaken
and making a fool out of myself
from the problem
the original wording of the problem
"find the growth rate at t=10"
t is x in this scenario
yeah you could think of it as that
up until this point the book im studying always sets “lim delta x approaches 0”
the problem is
you cant set Δt=0 directly 0
until you finish solving the problem
because of an issue
what issue?
we're also dividing by 0
Δt
so you have to wait until it's in an acceptable form to set equal to 0
ok, so continue where you left off
.
ok so from this part right?
oh
mhm
well once youre left with only numbers that are multiples of Δt in the numerator
you can cancel them out with the Δt in the denominator
yes
and you get some terms that do still have Δt
and some constant terms
the terms that still have Δt go to 0
so you can just erase them
cancel them
whatever
but the constant terms
turn out to be
-(300/30) + 5(20)/2
which adds up to 40
Mhmm
and the limit
alright
Yes
fancy math way of saying "LETS GO PROOF SOLVED HAHA YOUR MOTHER"
@tropic coyote
ok… now it should be correct
did I make a mistake here?
is my 3T^2/2 correct?
3 times delta t that is???
Wha?! 😭🔫
No wait, check my calculations
please
is 5 multiplied with delta t^2 + (- delta T) ^ 2 = 3delta t ^ 2 / 2?
alright let me check
yeah i think its right
checked more critically now
5Δt^2/2-Δt^2 = 3Δt^2/2
its right
Finally I can sleep in peace
nah its ok at least you got to solve it correctly
It’s actually night now, and my time has come to sleep
but I’m seriously considering staying up all night to read some crime & punishment and study
Well it’s not exactly something a neurobiologist would recommend😅
well lucky for you im not a neurobiologist
I want to have a good sleep rhythm
yeah i used to have a good sleep rhythm
like a week ago
idk why im staying up so late now
I wanna sleep consistently at 11 and wake up at 8, but I have so low energy when I do that
For some reason I’m super active at nights
same
also I have an addiction to discord cuz i live in a dorm
so I’m pretty isolated from everyone
cya there
Well, thanks for the help, whoever you is
im hsf, pro math sis B)
(explosion behind my back)
im play a LOL
@quasi glade you are familiar with the idea of factoring a polynomial into linear polynomials right?
Just the concept, not the computations
yea turning some qx^3 + nx^2 + nx + p
into x+n or somethin
i got that
got that all day
theres this one specific thing i been lookin at
yeah so basically, what this relies on is the fact that you can write whatever polynomial this is in the form $f(x) = (x-a_1)(x-a_2)\cdots(x-a_n)$
nHail
The product of a bunch of linear factors
When you multiply this out you will get $f(x) = x^n + \text{( a bunch of stuff in the middle)} + a_1\times a_2\times\cdots\times a_n$
nHail
so the last factor is a product of all the roots
So from here you can see a restricted version of the rational root theorem:
if you have integer roots, they must divide the constant term.
Does this make sense so far?
i think this is stuff i know
but
Ill show what i got
Synthetic division i think is the part of this is confusing me
Okay, the second half is a bit weirder, but it explains the part about the denominator dividing the leading coefficient
this is an exmple problem i got coming from some video i look up
this whole process
trying to find roots of that polynomial
that process at the bottom i dont get at all
I'll admit I'm rusty on synthetic division, I don't think I was ever taught that
but I can explain the rest of the rational roots theorem if you want
idk
do you think i should check the help channels
talk in there maybe someone will know whats up
Yeah you can try, if you have a specific problem
idk this could be a specific problem but it could also be a broad concept
You won't get much success there with "can someone explain this entire broad concept" though
yea
i must reiterate my reading comprehension SUCKS so #❓how-to-get-help didnt really do much for me
maybe perhaps youtube
my beloved
if you're struggling with synthetic division
start with polynomial long division
i know polynomial long division
synthetic division is pretty much a condensed version of that
how so
can you do polynomial long division for
(2x^3 -12x^2 + 22x - 12)/(x-1)
i can run that through rn
and there's also a mistake in that image you posted
Idk I just copied half of what I seen
either what you read was wrong, or you didn't copy it down correctly
boom get long divided
could be either, I just wrote that to convey my point
like what process I was yapping about
how do I get those numbers without doing the whole process
so the term being multiplied is just z from (x-z)
okay
its clicking
it is beginning the long and strenuous process of clicking
if it would be x-6 then the thing we multiply by would be 6 leading to
2 0 22 120 at the bottom
which would make a polynomial 2x^2 + 0x + 22 + (120/(x-6))
so that wouldnt be a zero would it
or a root
or whatever
cuz that last addition needs to be 0 if i recall right
correct
and x-1 would be a factor of the polynomial right
yes
(2x^2 - 10x + 12) * (x-1) in the end
right
finally makes sense
i completely missed that unit last year I appreciate it
can someone help me understand a problem that I’m facing?
If you'd describe your problem, the odds of someone being able to help would be much higher.
Right
So here is my problem
f(x) = -x^2 + 2x
find the tangent line at (2,0)
oh my bad
Does anyone know how to do this?😭
trigonometry?
i dunno, all I know is SOH CAH TOA
lol
!da2a
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question! See https://dontasktoask.com/
They were already told that and posted their problem and moved to #calculus and got help there.
Take the derivative of f(x), and then plug in your point to fine the gradient. Then solve y=mx+c.
aight bruh, habit
idk man, i learnt this stuff in precalc
did you end up finding it?
Yes, appreciate the help though
I have a question will anybody be able gto help me
A can do a piece of work in 10 days and B can do the same work in 15 days. If they start working toga=ether then in hiw many days can A and B can complete the work?
no. S= rθ (Help meee)
bruv, I have no clue
I have my own shi to solve
do you need/want help with this or not...?
Do you know the answer for x I am getting the answer
Anything to the power of 0=1, so the inside of the log is equal to 0. Then solve for x.
log is undefined when the input is zero
Ain't it sqrt(3) to what equal that term is 1 so we have to equate that term to sqrt(3)
No, x^0=1
But as transparent elemental said log with input 0 is undefined
What?
Like log base a input b means what to the base a equals b
So nothing to the base is equal zero
You can just do sqrt(3)=(inside log)^1.
Yes, I wrote that at 2am, so I apologise.
Bro I wasnt even responding to your question.
I am saying did you got the same solutions after solving it again
Idk bro I’m in my bed at 3am listening to MF DOOM and reading manga. I do not have it in me to do mental math.
The current time for blunder69 is 10:31 PM (IST) on Mon, 11/12/2023.
It's time for me to sleep btw
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Kk
Whats difficulty is coming in solving 24sin^2x=24-12cosx
you can divide by 12 at the start, should make things a bit easier.
try omitting the + 2πn in each one
you only want the solutions in [0, 2pi) not the general solution
can't tell if this is the only mistake but it is at least one
After dividing by 12 both sides just put sin^2(x)=1-cos^2(x)
It will be a quadratic in cosx
Not cos^2
What it's an identity sin^2(x)+cos^2(x)=1
I am saying to use that identity
That just feels like over complicating.
x^(1/2) is square root of x. Square root of 0 is ...
Formulas of log: Let a, b > 0 and s be any real number.
definition of log: aˢ = b ⟺ s = logₐ(b). in particular, logₐ(a) = 1 and
common log: log(a) = log₁₀(a). in particular, log(10) = log₁₀(10) = 1
change of base formula: logₐ(b) = log (b)/log(a)
product → sum: log(ab) = log(a) + log(b)
power → multiple: log(aˢ) = s log (a)
limit of a sum is not equal to sum of limits in this case
(not that limits have anything to do with infinity arithmetic in the first place)
think: $\bZ \setminus 2\bZ = ?$, $\bZ \setminus (\bZ \setminus {1}) = ?$
On the other hand, the limit of -a + (a+1) is 1, and the limit of (100-a) + (a-58) is 42.
Knowing that two seqences diverge to -infty and infty is not enough to know how their termwise sum behaves.
So such limits would not be a good argument for defining a meaning for (-infty)+infty.
is there any way to find the vertex here? how can I use the points?}
hey every one i am a little confused what is considered precalculus
It's a chiefly American term for a loose collection of high-school topics about (single-variable) real functions that can be taught without using the concepts of derivatives.
The basic concept of function; graphing functions; asymptotes; domains and ranges; maxima and minima, monotonicity; sometimes linear functions; particular functions of mathematical importance (trig functions in radians, and their inverses, exponential functions and logarithms, rules for manipulating those). Sometimes a basic non-rigorous introduction to limits is given, at other times that seems to be postponed to actual calculus.
The name seems to indicate it is usually taught from a perspective of "don't even think this will be interesting or useful in itself, it's just a bunch of stuff you need to ~~know ~~ be able to do before you get to calculus".
it seems that you’ve already determined that this can be modeled by a quadratic function, whose graph has reflection symmetry along a vertical axis. knowing this, do you see any 2 profits that are equal? and what does that help you conclude?
help
Hey, would you mind giving a translation for each question? Without knowing the question I don’t have a way to help you.
how those are equal
<@&286206848099549185>
2CC = C+C
I.e, 2CosxCosy=Cos(x+y) + Cos(x-y)
Can someone show me how to do this question without graphing it.
A sinusoidal function crosses its minimum at ( 20 π , − 10 ) and then the next key point, its center at ( 24 π , − 8 ) .
a) Create a sine function that models this graph
b)Create a cosine function that models this graph
i know my amplitude is 2 and vertical displacement is -8, how do i find period and phrase shift?
i definitely just failed my precalc final

Skill issue
Sorry to hear that :(
i think i also failed my precalc test 
I mean I won’t know until it’s graded but for sure did not study enough for the test I have an 95 currently in the class I’m just really wanting a 4.0 this semester
LET'SSSS GOOOOO i PASSED AND KEPT MY A
where is sine maximized?
A and B will be the same distance from this argument
sure
so sin(C) = max -> C=pi/2
how far is A from C?
how do we know that B and A are the same distance from C?
pi/4?
since they're equal to each other
,calc pi/2-pi/5
Result:
0.94247779607694
noo
this is wrong tho
wait so its 3pi/10
so i add that to pi/2 to get b?
since its the same distance
so it would be 4pi/5

I'm kinda lost
On the right side you have to simplify. Then use log(a)=log(b) therefor a=b rule.
Make sure the coefficients of the logs are the same
I need help with this problem
Think about what you need to have a vertical and horizontal asymptote
Well how would you go about solving it
the question mentions k but it is not given in the function
are you sure that there is no printing error
oh my bad
This is the full problem by the way
for fx to have horizontal asymptote at y=0, the function fx must approach 0 as x approaches infinity
no
just compare the degree of numerator and denominator
we need y =0 for x approaching infinity
which means we need an x in denominator
degree of numerator<= degree of denominator
therefore k+2<5
k<3
Wait but I thought 3 was wrong
But how would we get that answer
my mistake
I did what you did
there would be no = sign in k+2<5
if there were an = sign then we would get k=3 and asymptote at y=1
we want asymptote at y=0
hence k+2<5 and not k+2<=5
@woven compass you were typing
how do i learn limits
There’s a few ways, you can learn formally in your class, you can read a textbook, or you can watch videos on YouTube (Organic Chemistry Teacher and Khan Academy).
well
my teacher is pretty bad
the organic chemistry tutor is good
and khan academy i use too
but its confusing at times
textbooks dont really help
thing is
the school syllabus is pretty rushed
and it has the randomest stuff
and i have a test this week is why im concerned
How is the teacher bad?
rushed
gives us too much and unnecessary infromation
hard to process
and doesnt really care about every student
Dam that sucks
yeah
Limits are pretty easy though
If you are new to calculus the tldr of limits is just plugging numbers into the equation as they get closer to the number you want to actually plug in.
Take $\lim_{x\to0}f(x)=\frac{1}{x}$
TheLord26
Just plug in small numbers
You might start with f(1)
Then f(0.1)
Then f(0.00000001)
And you will see a pattern
As x gets smaller f(x) gets bigger
😭
So you then say the limit approaches infinity
There’s more advanced ways but for that I would highly recommend watching lectures on YouTube and working through text book questions.
?
I don't really need help but like a tip
I have a ACT coming up
february ?
and I heard 12% of time pre calculus question is asked on it
I have no clue how to solve them
just want some tips to solve without even looking at it
yeah
good luck
thanks
last time I got 26 on ACT math
hoping for 30 or 31 this time
for realsies
In February should give you some time to start studying, but if you want to "solve without even looking at it", you're out of luck from the beginning.
i know but any tips


