#help-10
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.close I give up
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can someone teach me how to find the coefficient of x^n in a power series
i am trying to solve it for f(x) = 1/(1-x^2)^2
in such cases where its just x^2 or some other power plugged into a function, its often easier to first do 1/(1-x)^2
which you can either do by computing the taylor series or by integrating and recognizing something
ok got it but what do i do after that?
wdym. afterwards you are done
no but what im trying to find is the coeffiecent of 1/(1-x^2)^2 not 1/(1-x)^2
its the same series
just x^2 plugged in
so instead of (random numbers) 1+3x+7x^2+15x^3 or something its 1+3x^2+7x^4+15x^6 etc
ahh okay got it thank you, i thought it would change the coefficent for some reason
thankfully not
okay thank you 🙂
@carmine sable Has your question been resolved?
but hold on considering this for n's the x^n's become only even so does it mean that when n is odd the coefficent will be just zero?
yes
so the coefficent is (n/2) +1 when even and just 0 when odd then
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@carmine sable Has your question been resolved?
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Guys how do I solve exponential equations
😂
your pfp is so cool
I can drop the image if you want
dont mind
show an example
^
All I want to accomplish today is develop an understanding of these equations
Like the ones on the SAT a
Knief i haven’t even started precalculus and i’m trying to learn how to find the derivative in a function
yea but learn the fundamentals first
this?
I can’t find where to find the elementals
yeah sorry my autocorrect is annoying
Basically i’m trying to master algebra and geometry before sophomore year and before december
I have the shsat soon
tbh i didn’t do SAT specific studying so i wouldn’t know
i took some practice tests
that’s it
oh you’re young
you’ll be chillin
Yeah but i’m trynna learn all of that right now
if you want to get unnecessarily good at geo and algebra then pick up the AOPS books
My “peers” are doing precalculus in their freshmen year
I never heard of that, AOPS?
ahh you go to an advanced school
art of problem solving
they have subject specific books
more for competition math
but still useful
My friends do, but unfortunately life dealt me the wrong cards and I am in the worst DOE school in all of new york
i’m in new york
I am solely depending on the shsat to get me out of this school
unfortunate
Cool, i won’t have to unnecessarily explain why I take the regents lol
you’re in a better spot than most at your age though
i barely took any regents
only junior and sophomore year
covid for freshman and 8th
Oh, I guess that’s what happens because of the pandemic
But feeling smart by DOE standards amongst those who don’t care at all isnt useful to me
Living environment is annoyingly long
yea living environment was just boring
didn’t give a shit about finches
earth science was wack too
its more like the idea of biology lol
i didn’t have to take either
earth science is 10th grade?
I took the global history regents a while ago
My goal is ALL AP CLASSES
and self studied for ap physics 2 and physics c e&m because my school didn’t offer it
nah you don’t want ap latin and all of those
just take all of the science, math, and history
More appealing for colleges
stem classes are where its at
fr
i credited out of the first two years essentially
of college because of my ap credits
Its just my teachers lack the ability to explain ANYTHING
learn on your own
regardless of what it is, they don’t care about the students
I’m trying, kinda directionless for the most bit
start with khan academy
then whatever subject interests you after, just go on youtube to find books and or videos
mit ocw was always good too
but with what you’re doing khan academy is all you need
What if i’m still lost 😂
but i’d supplement with a lot of problems
do more practice
I can’t find any practice questions or tests because they are all subscriptions
there are books online
openstax probably has some algebra
they’re open source
yea i checked
they do
they’re great
I’ll check it out
they have everything up to calculus 3 i think
full textbooks with exercises and everything
all for free
What would you advise me to do
do more problems
watch videos on khan academy/youtube
and use textbooks online
no need to spend money
I’ll do my best, thank you
you’re welcome
Just sharing my thoughts:
Before i was in this math discord, I thought that I am good at math 🗿 but now that I think of it, I’m not that good compared to most people 😭 I’m only better than my classmates back in junior high (grade 7-9)
I lack knowledge in many math topics. The highest math I’ve studied in highschool is pre-cal
And then I took accounting in college 🫠
ping?
there’s always a bigger fish
@warm depot Has your question been resolved?
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This is a practice exam I'm looking at, can someone explain to me whats going on in this problem?
I know that the FTC says that the derivative of an integral is just F(x), so whats going on here?
FTC tells you that if F is an antiderivative of $f$, then $\int_a^bf(x)dx = F(b)-F(a)$
rafilou is not not born in 2003
so just let $F$ an antiderivative of $2\ln(t)$
rafilou is not not born in 2003
$g(x) = F(e^x)-F(1)$
rafilou is not not born in 2003
now we differentiate, and we need chain rule
I think you mistook with another version of the FTC that says that $F(x) = \int_a^xf(t)dt$ is an antiderivative of $f$ when $f$ is continuous
rafilou is not not born in 2003
notice that the lower bound is ALWAYS a constant, and the upper bound is ALWAYS the input x
which is not what we have here
since the upper bound is e^x, not x
so this version of FTC is not applicable
@remote pivot Has your question been resolved?
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could anyone help me with this?
i thought the "trend" should be the other direction, since as t increases, x is approaching 0 while y also goes up
why is the "trend" given in the soltution says its from left to right, not the other way
t=0
,calc e^0
Result:
1
,calc 3*e^0
Result:
3
Result:
0.36787944117144
,calc 3*e^-1
Result:
1.1036383235143
did you know calc is short for calculator
its just a fun fact i learned back in the days
yeah?
me taking calculator 3 in college
Managed to find the only flaw in my arguments procks to you
I thought it was props to you?
that's fair. spam, king
hmm guys? Are you here to answer my question?
^
honestly in a vacuum, I like your interpretation of how it should be more, but a variable doesn't have to change in just the positive direction I guess
actually, I don't know what the point of the arrow heads in the first image is. they seem irrelevant
i only just started parameter topic, so what what does the "trend" represent here? Just point
it's not even the curve on (0, inf)
oh, then what does the arrow usually mean
it usually does denote how a point on a curve moves as a parameter changes
yeah, thats how i interpreted at first.
this is the orignal question btw
maybe they just wanted to illustrate its the same graph as y=3\x?
I think so
except with some restriction
but is there another figure? neither of these are the actual curve, they show too much
you're right to be, it should be equivalent to the function f : y = 3/x, 0 < x < 1
i thought its supposed to be like this? purple curve
starting from the point (1,3), the x-coordinate shrinks dramatically but never reaches 0, and the y-coordinate rises dramatically
as per the given parameterization
i guess the one pointing right and approaches y=0 is when t<1?
more generally t < 0
you cut out some middle section if you say t > 0 or t < 1
allowing t to be any real number gives the curve of figure 7a, the left one
ah yeah
so could you agree my interpretation is correct?
^
yeah, the purple section should extend arbitrarily leftwards/upwards, but you highlighted what you'd actually see in the window
I already gave it the nonverbal thumbs up lol
endlessly and not touching zero right
yeah
yeah ik i just want one more confirmation
no problem
thank you so much for answering
no problem part 2 lol
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Right so I'm studying and I am after completely forgetting how to simplify quadratics, can someone help?
Yoo
hiya!
Thats text and texts
correct
yeah
and those two numbers when added have to also make 11?
yes
so now what do i do after that?
well actually since the x^2 has a coefficient
thats bigger than 1
you have to do a little more
oh its the other one
sorry could you do a little explaining for me my minds gone blank lol
sure
thank you so much
so you have to also take into account the multiples of 6
which are 3 and 2 and 6 and 1
and how do i know which one to use
trial and error honestly but id start with 3 and 2
remember since the coefficient is 6 we actually have to find numbers that multiplies to -60
👍
thats 2x + 5 i can do the bottom its just the top one i cant do
thank you for the help!
nice
.done
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this is a physics exercise but i think this is math-related
could someone explain to me how the first equation becomes the second one, please
thank for your help really much
I found an explanation online i understand everything before these lines
shouldn't it be v(t) = e^(-b/m)t + v0 (take e both side) instead of v(t) = v0e^(-b/m)*t like this ?
@ripe leaf Has your question been resolved?
it is taking e on both sides
but e^(a+b) = (e^a)(e^b)
not (e^a) + (e^b)
thank you i got it now
np
@ripe leaf Has your question been resolved?
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Hi can someone help me with this question
Alright so what have you tried so far
Alright so let’s try writing out the function
If y is the mass of the population, we can write the function y = 3(2)^x
And what we’re asking is
For what value of x is y = 60?
!nosols
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
._.
First time as a helper and I’m already getting reported 😭😭😭🙏
._.
nah you’re chillin gigagoat
low key, i think Rav just wanted the answers from my goat
manless universe
real
dw
you didn’t deserve this
My first student ditched me 😢
hate it when a helpee leaves
yeah, i would ditch u too ngl
the audacity
real
damn
Why isn't this $P(t) = P_0e^{kt}$?
harsh
Bean Man
???
Bean Man!
nice try bean man!
wait
then doubling every hour is consistent with Gigagoats model
I think there’s a command or something
because it takes a long time
i can close it
okie
but i wont
i see
yea
okay imma close it
go ahead!
.close
oh
🙏🏻💀💀
Uhhh
Something isn’t right 💀💀
i think only Rav can or smth
Maybe it’ll work the second time
I see that gigagoats is correct but I'm asking why is what I typed wrong
.close
sorry i was afk
He’s back!!!!
i had pings off
Ok Rav
for some reason
Rav, we missed you
My first student!!!
srry lol
it isn’t
we forgive you sir
now everyone let gigagoat cook
What have you tried so far Rav?
so i said let y = 3^t
and then if y = 60
then 60 = 3^t
but idk where to go
from there
Well, we know that every hour, the population doubles
Does that make sense with your function?
not really
So what do you think your error was?
do i have to do y = 2^t x 3?
Yes!
Because 3 is the initial population, and because it doubles every hour, we have 2^t
20 = 2 ^t
Yes keep going
log2(20) = t
Yes you’re on the right track
log10(20)/log10(2)
Yes
Perfect!
how do i convert from decimal to minutes and hours tho
Do you have the image of the original question
I don’t think it requires you to express it as minutes and hours
It should be fine expressing it as a decimal in hours
≈
the answer book has it in minutes and hours
so i wanna know how to convert it
to that
oh
So what do you think you should do differently
19.3156856934
Everything in the tenths digit and below is less than 1, so we only convert those into minutes
Yes
Ye
ty for the help 🙂
Thank you 🙏 🙂
Gigagoat the true goat fr
real
I did itttttt
ill close now
My first student
.close
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hi
answer was
a) lambda=2 and lambda=-2
b)lambda = 1
c) labda in R except above values
i understood why
.close
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Can someone help explain how this is E
I understand that inverse proportion is where a=k/b
K=p x sqrt(m)
If you substitute it doesnt sqrtm cancel out to p=p
Or does that not matter
And we just test it
I have no idea what you're substituting
You should be substituting your 3 pairs of numbers
@silent acorn Has your question been resolved?
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How do I begin this?? Do I use intermediate value theorem??
yea that would work
How do i start exactly?
If f is continuous on (a,b)
Then its also continuous (ri, ri+1)??
sure
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Lemme claim this
So.. uhhh can you like explain one by one this question and answer
question: log 10 = 1
answer:
2 - log 5
2 log_10 - log 5
log 10^2 - log 5
log 10^2/5
log 100/5
log 20
um what ?
What... do you not understand?
$\log_{10} 10=1$ is not really a question
convergence
You question is a bit incomplete. It should be Calculate/Simplify 2-log_10(5) using log_10(10) = 1
Hello
That seems to be the step 1 of the answer, and not the statement of the question
Whoever wrote it doesnt seem to have written the question here
Red is just a fact
Yellow is the solution
Their is no question here
Just a fact
And a solution
IDK OKAY It's like that on the board I don't know what to tell you guys 😭
To some arbitrary question
This or a statement equivalent to it should be the original question for this solution
alright so log_{10} 10 =1 so 2=2log_{10} 10
It is important to understand the question before understnading the solution
You dont have to tell anything. We are making sense of the stuff in the pic, and letting you know what is and isnt in there.
There is no question 😭
But to the image at hand
Do you understand why log10 = 1?
Yes... That circled text is the question
I think the question
2 - log 5 = log 20 can be log 5 x 2 = 20 = log 10 = log 20 to match the right side
Is that correct?
No
what do you mean log10 = log 20 here?
Well since the solution (step 1) here is log 10 = 1 I could just multiply 5 x 2 together
tbh individually all the equalities that you have written here are wrong in
log 5 x 2 = 20 = log 10 = log 20
log 5 x 2 = 20
log 10 = log 20
That is fine, but that gets you log(5) + log(2) = log(10)
This doesnt mean log(5x2) = 20
Or
log 10 = log 20
that doesnt help us much
log 5/2 = 20/2 is still wrong
Can I try and explain what is being done in the image?
Yes
Yo
Ok
What’s going on here
So in the first step here
🪵
Ah I see
They took log 10 = 1
What’s the questions
How did log 2 - log 5 = log 10 became log 10 = 1?
They didnt do that
Huh?
there is no log2 to start with
???
What they did was, they wrote 2 as 2 * 1
@rose scroll what’s the original question
His trying to explain how did the solution from the photo happen
@stiff mortar this is the question
So... just,,, 2 * 1?
Yes
So log will be 0?
so 2 becomes 2*log10
nonono
Wait, we will get there
So...
do you first of all understand how 2 and 2*log10 are equal?
2 - log 5 = 20
2*log10 5 = 20?
Pretty sure that’s correct working out
It is correct, she wants explaination for steps
Ah ok
Uhhh
The steps say
2 - log 5 = log20
2*log10 - log 5 = log20
OHHHH SEPARATE
Yes
Okay okay I got it
So how do you go from 2 - log 5 to 2*log10 - log 5?
I think the separate doesnt mean what I think you mean.
Because log base 10 of 10 is equal to 1
Thats what I meant by 2 = 2*1 = 2*log10
So 2 x log10
What happened to 2 - log
when two things are equal, like log10 = 1, you can replace one of them by other
Nothing has happened to it. We are only looking at 2 from the eexpression 2 - log5
log5 is a nice guy, and we have no trouble with it
2 is a bad guy coz he has no log
So... we have to times it to a log?
so we need to give it a makeover so 2 also has a log
yes
anything times 1 is the same number
Okay
and we know log10 is just another way of writing 1
so we can multiply 2 with log 10, and it still remains 2, but now has a free log term
It’s just some manipulation of formulas. Usually you want to make it easier for you to group terms or whatever so replacing something with another that is mathematically equal is a good thing
that log term helps us apply rules of logarithms to it
Sooo What do I do now?
Do you get why 2 is same as 2*log10?
Yes
Then you can apply an appropriate rule of logarithms so that 2*log10 becomes log(10^2)
can you name that rule?
Okay next step
Now on log(10^2) - log5, you choose to apply another law of logarithms
Can you tell what you should use here?
Quotient Law is the closest when I analyze this
Yes
So.. log 10^2/5?
Correct
Also, use that 10^2 = 100
so you get the expression log(10^2) - log5 as log(10^2/5) which becomes log(100/5)
Now can you tell what you do here?
There you go, thats the answer
One second, while I make up a problem ok?
kk
Prove that $\log_{10}(4) + 3 - \log_{10}(5) = \log_{10}(800)$
Bacter10Fr4g is not fr0g
@timid silo Heres a new problem, very much similar to the previous problem
@rose scroll
Its correct
Lemme get my power bank real quick and picture the next one
Do you know all these rules of logarithms?
Its just using the product rule and quotient rule on the equation
You have the wrong expansion written in 1.
It should be $\log_{b}(x\cdot y) = \log_{b}(x) + \log_{b}(y)$
Bacter10Fr4g is not fr0g
I'm confused cause I thought the quotient law goes something like
Log 4y^8/Z^3X^2 = Log 4y^8 - Log Z^3X^2?
Oh okay
Yes, it does. You are right. Thats what is written there too
Log 4y^8 - Log Z^3X^2?
So I guess since there is z and x I should separate everything like
Log4 + Logy^8 - Logz^3 + Logx^2
Correct?
then.. For the exponent I guess put it like
Log4 + Logy^8 - Logz^3 + Logx^2
log4 + 8*
logy - 3*
logz + 2*logx??
Sorry I have to keep separating em cause it looks like this
Me and My boyfriend agreed to like take breaks :p
yea
So it's correct?
you should use \ and * together so it looks properly like what you want e.g. 8\*logy
Okay
Thanks
I'll take a break then come back
Is it okay like while I'm back I could answer a similar question?
Okay then thank youuuuu
npnp
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I'm back
.
What-
This is occupied
whats the question?
that seems correct
i dont understand ;-;
Can you give me a question similar to the encircled question? I wanna practice.
My brain is literally dead right now
Give me around half an hour
<@&286206848099549185>
Nah it's fine
Would you like to continue with this (sorry for the ping Kreutzer this is for all helpers who would like to help me at this time)
or
Give me a question similar to the encircled question?
You need change of bases formula for solving this
which you said, you havent been taught
oh
so its fine if you dont get this right now
We might as well get another question
So that we can follow this
You can solve this:
$\log_{10}(x) + \log_{10}\left(\frac{y^2}{x^3}\right) - 3 = ?$
You need to simplify this expression so it all becomes a single term
Bacter10Fr4g is not fr0g
The answer you should get is $\log_{10}\left(\frac{y^2}{1000x^2}\right)$
Bacter10Fr4g is not fr0g
YES 
How about next time without telling me the answer because I kinda figured out very easily on what answer I should go for ;w;
Meaning It's not challenging
Can you find me another question similar to it?
Bacter10Fr4g is not fr0g
Simplify this
(You dont have to evaluate the numbers. Just use the laws of logarithms more times)
You can start again, by first using the product law everywhere
Your first step was good, but you started messing up near the end
Are you trying @timid silo ?
Nooo
Why do you split 5 log_10 (z^2) as log_10 (5) + log_10 z^2 ?
Can you tell me what rule that is?
if you dont know then you shouldnt write it like that
cmon, use power rule on 5 log(z^2)
and tell what should be the answer
you know you can do it
You have to use the 3rd rule
From power rule
what
you do know the power rule right?
Yes
Why is z^2 log_z^2 instead of log_10?
log_10 is the base of log
anddd???
....
You know how log and exponent are related right?
10 in $\log_{10}(z^2)$ is same as the b in your notes. The rules do not apply to 10.
Bacter10Fr4g is not fr0g
z for real numbers is absolutely cursed
hey, an unknown can be anything ok? Doesnt have to be x or y all the time. You can use z
NO. Leeave the 10 in log_10 alone
do not touch the 10
yes i am aware of that but...
There is only one thing. Not playing with the numbers written in subscript. Leave the 10 in $\log_{10}(z^2)$ alone. No playing with that 10. That means do not multiply it. Do not divide it. Do nothing
Bacter10Fr4g is not fr0g
Okay
just keep the fact the base is 10 in the back of your mind for now
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I am having trouble with how to define this thing so that /0 case never is and I don't know what to do for from end with 2d as said to substituting in an integral for a straight line. I think I can define arbitrarily a set of points all is relative to such that no divided value is zero but that v_2, is that a point or a number? How does it go to end result like this: https://mathproblems123.wordpress.com/2022/09/13/integrating-polynomials-on-polygons/ ? @worn coyote, sorry, you did this, so if you want to weigh in, go ahead. Using Green's Theorem on a planar, straight line, closed, not self intersecting polygon in 3d+ space. I prefer to avoid division as it can be undefined. Sorry for all this, just those "pictures" inside should be enough. Actually, dot product make numbers but v1 is a point so multiplying gives another point so yes v_1 and v_2 are points. I guess all I need is how to go from that Green's Theorem end to substituting into that integral from 1 to 0. X E.
Kind of sorry to do this, but I can't explain not understanding to a computer like this very well. X E.
@primal iris Has your question been resolved?
Would it be like inverse of partial derivative of a function over partial derivative of x?
@primal iris Has your question been resolved?
f(x,y)=sqrt(sum per 3d+ dimension (O+Xx+Yy-P)^2). X E.
Polygons are straight line, planar so like 2d, closed, and not self intersecting. X E.
Should I just focus on triangles, rectangles, circles, circle parts, lines, and points because I think I can do all those?
Just realized, need polygons. X E.
Hi, sorry for late response. I've just returned home
Okay. Thanks for eventually coming. X E.
Admittedly, yesterday I did a poor job at explaining the idea
Hopefully today I will manage to properly explain everything
Let's start with reducing the problem to 2d. You mentioned that v_2 may encounter division by zero. In reality, that's not the case if p_1 - p_0 and p_2 - p_0 are linearly independent.
Since p_1 - p_0 and p_2 - p_0 are not collinear, they're linearly independent and therefore v_1 and v_2 are well-defined.
Okay so are we defining p1 relative to p0?
Yes, but yesterday you said that p0 = (0, ..., 0) so I started saying p_1, p_2 instead of p_1 - p_0, p_2 - p_0
Oh, p0 can be 0s but not necessarily, should I define things so p0 is 0s way for this?
Sorry, I was bad at explaining. X E.
p0 is (0,0) in 2d though. X E.
Well, we can let p0 be any vector, that doesn't complicate anything
Here's an image
The red vectors are p_1 - p_0 and p_2 - p_0
Then we orthogonalize them and get v_1 and v_2 (I will send an image in a moment)
Thanks for all this. X E.
v1 and v2 are orthogonal to each other and have length 1. That will be convenient later
So what are v1 and v2 equations?
Just like yesterday
Okay, got that. X E.
$v_1 = \frac{p_1}{||p_1||}$, $v_2 = \frac{p_2 - (p_2, v_1) v_1}{||p_2 - (p_2, v_1) v_1||}$
EQUENOS
Oh, wait, we now have arbitrary p_0
$v_1 = \frac{p_1-p_0}{||p_1-p_0||}$, $v_2 = \frac{p_2-p_0 - (p_2-p_0, v_1) v_1}{||p_2-p_0 - (p_2-p_0, v_1) v_1||}$
EQUENOS
Here we go
Working so far. X E.
We now can calculate the coordinates of $p_k$ in terms of that planar basis
EQUENOS
It's simple: let $x_k=(p_k - p_0, v_1)$, $y_k = (p_k - p_0, v_2)$. Then $(x_k, y_k)$ are the coordinates of $p_k$ in our orthonormal 2d basis
EQUENOS
Those , are dot product correct?
yes
Try *?
I can use this notation, if you want: $x_k = (p_k - p_0)\cdot v_1$
EQUENOS
Easier to see it is dot, not , like another coordinate thanks. X E.
alright
I can tell this will be complex. X E.
Now let's recall the original goal. Let $\Omega \subset \mathbb{R}^n$ be a planar polygon, and let $f: \mathbb{R}^n \rightarrow \mathbb{R}$ be an integrable function. The goal was to compute
$$\int\int_{\Omega} f(p) d\sigma,$$
where $d\sigma$ is the element of the area.
EQUENOS
Yes. X E.
We now know that each point on the polygon can be expressed as $p = p_0 + x v_1 + y v_2$, where $v_1, v_2$ is an orthonormal basis, so the integral got reduced to
$$\int\int_D f(p_0 + x v_1 + y v_2)dxdy$$
EQUENOS
Here $D$ is a polygon on the xy-plane that we obtained after calculating all $(x_k, y_k)$.
EQUENOS
I notice that vectors v1 and v2 are more like of 1 or less any dimension, can be greater than 1 distance. X E.
Or am I wrong?
$v_1$ and $v_2$ are vectors of length precisely 1
EQUENOS
Okay, sorry. X E.
And they're perpendicular to each other
That follows from this construction
Anyways, let's continue
For convenience, let $F(x,y)=f(p_0 + x v_1 + y v_2)$.
EQUENOS
Next?
Due to Green's formula, if $F(x,y) = \frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y}$, then we have
$$\int\int_D F(x,y)dxdy = \int_{\partial D} (Pdx + Qdy)$$
EQUENOS
Let's just say that $P(x,y)=0$ and $Q(x,y) = \int_a^x F(s,y)ds$.
EQUENOS
Then, if $(x(t), y(t))$ is the curve that parametrizes the boundary of $D$, our integral is equal to
$$\int_0^T Q(x(t),y(t))\dot{y}(t)dt$$
EQUENOS
I don't know what that s does but this seems maybe correct. I can do single integrals. X E.
Since $D$ is just a polygon, the curve is a piecewise linear function, where the $k-th$ segment can be paramterized as $(1-t)(x_k,y_k)+t(x_{k+1},y_{k+1})$
EQUENOS
s is just an integration variable
For example, if $F(x,y)=xy$, then $\int_a^x F(s,y)ds = \int_a^x s y ds = \frac{s^2 y}{2} \mid_a^x = \frac{x^2 y}{2} - \frac{a^2 y}{2}$
EQUENOS
Shall we continue from here?
So now we have
$$\int_{\partial D} Q(x)dy = \sum_{k=0}^n \int_0^1 Q((1-t)x_k+tx_{k+1},(1-t)y_k+ty_{k+1})(y_{k+1}-y_k)dt$$
EQUENOS
In the blog post you shared, the person was integrating monomials. Let's do that too, because why not. Let $F(x,y)=x^p y^q$. In the formula for $Q$ we're free to choose any $a$. Let's choose $a=0$. Then we have
$$Q(x,y) = \int_0^x s^p y^q ds = \frac{s^{p+1}}{p+1}y^q |0^x = \frac{x^{p+1}}{p+1}y^q.$$
After that we obtain
$$Q\left((1-t)x_k + t x{k+1}, (1-t)y_k + t y_{k+1}\right) = \frac{((1-t)x_k + t x_{k+1})^{p+1}}{p+1}((1-t)y_k + t y_{k+1})^q$$
Now we can just substitute that to our sum
Inside the integral "," separates two arguments of Q
Oh then solved already?
EQUENOS
yes
You now have the algorithm for integrating f(p) over polygons in R^n
I am on a phone, have to wait for internet to be online again, then I will document this on a computer and hopefully have no more questions. X E.
Alright
So partial derivatives went away?
Yes, here's how we dealt with them: #help-10 message and #help-10 message
Okay, there will be a pause but going to document now. X E.
okay
I think I got it, if this does not work then I may call you or someone else again. X E.
That T above is like x in F(x,y) correct?
Anyway, thanks. X E.
.close
Closed by @primal iris
Use .reopen if this was a mistake.
T is some upper integration bound that depends on the curve we chose. I meant that (x(t), y(t)): [0, T] --> R^2
So if we integrate over such curve, the integral is from 0 to T
.reopen
✅
I still am unsure what happened to |partial derivative p/partial derivative x+partial derivative p/partial derivative y|. X E.
As from origin formula. X E.
This looks as solved as it should be. X E.
Great, power out, no internet. X E.
Just so you know, those last two not from now. @worn coyote . X E.
oh ok
We want to find $P(x,y)$, $Q(x,y)$ such that $F(x,y)=\frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y}$. Note that if we let $P(x,y)=0$ and $Q(x,y) = \int_a^x F(s,y)ds$, we're done. Because in this case $\frac{\partial P}{\partial y}=0$ and $\frac{\partial Q}{\partial x} = F(x,y)$, so we indeed have $F(x,y)=\frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y}$.
EQUENOS
Before that, p as in f(p(t)). X E.
$F(x,y) = f(p_0 + x v_1 + y v_2)$
EQUENOS
Each point on the original polygon can be represented as $p_0 + x v_1 + y v_2$
EQUENOS
So integrating f over the polygon is equivalent to integrating F(x,y) over D
Looks like we re-defined to this. X E.
Also this. X E.
I guess solved. X E.
Any closing words?
No I guess. Thank you. X E.
Maybe write a paper on this one EQUENOS, this is great stuff for graphics. X E.
I think the morale is that as long as we have a planar figure, the integral over it can be reduced to a 2d case
I guess I have permission to use this in a 3d+ graphics system?
I think a more meaningful generalisation of the blog post you shared would be to integrate over polyhedrons, but again, all this was invented long ago in far more general cases, such as manifolds of arbitrary dimensions
Of course
Now fun part, how to tell a computer this. X E.
I'm gald this problem has applications in computer graphics
I get to do that. X E.
Even more fun when I need to calculate where plane is in view in 4d+. X E.
Anyway, thank you. X E.
It's a painstaking work but it's definitely doable
You're welcome
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What are the number of 10 digit binary sequences such that no more than two 1's or 0's are placed beside each other
Example :
1001101001 --> ✅
1101011101 ---> ❌
should be 2^n - (number of sequences in which there are 3 1s in a row or 3 0s in a row) right?
since if there are 4 in a row, there are 3 in a row for example
so no need to count those
actually can you tell me how we can approach the 3 1s or 0s in a row problem without repetitions?
cuz my approach initially was that we group 3 1's or 0's in a box then we place them in between a series of 7 digits like so
1010101 ----> place -----> 1010[000]101
but then this as well as this are same
1010101 ------> place -----> 101[000]0101
these two cases are equivalent and so will be repeated
that's a good point, I think you may have to do it by considering cases in which there are exactly 3 zeros in a row, exactly 4 in a row, etc.
there's probably a simpler way but i can't think of it right now
oh duh, just methodically count the number of sequences with exactly two 0s in a row
same for 1s, it shouldn't be too difficult
but then placing will be tough as we cant place [0,0] near another 0 or [0,0]
start with only one 00 and count those, then two 00s, then three 00s, etc
if there is only one 00, then you know there must be 1s on either side of it, and the rest of the digits must be alternating
does that make sense?
yes

