#help-28
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can someone check my answer please
What if you did not get the answer right
is there a punishment or sth
yes 100 lashes
really? Im being serious
my grade drops
I see
does it affect you to get into a good college in future
yes
I suppose it only depends on the test result?
can you just check my answer man
curiosity has predominated my mind
are you finna help me ?
yes
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assuming h is height and t is itme in seconds, what is the maximum height?
h=-5t^2 +15t +0.5
Please don't occupy multiple help channels.
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Alrighty
so we have:
y / (1-y) = c * e^t
How do we isolate y? Is this even possible?
Because they want teh equation in terms of y, but I don't see how to isolate y?
u can multiply both sides by (1-y)
not quite
y = (1-y) ce^t
=> y = ce^t - ce^t * y
=> (1 + ce^t)y = ce^t
I was thinking of
y / (1-y) = c * e^t
y = c * e^t * (1-y)
1 = c * e^t * (1/y-1)
1 / (c * e^t) + 1 = 1/y
y = 1 / (1 / (c * e^t) + 1))
but my way seems more error prone & much uglier
you are right on both counts
I think i'll take a stab at sleeping
and then hound the MATH_HELP chat
With Linear Algebra Problems tmmw
🤩
so excited wooooo
@jolly anvil Has your question been resolved?
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idk how to solve
@rocky saddle Has your question been resolved?
Have you tried solving for alpha and beta?
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Hello, does someone know how to solve the following question?
i do not believe it is reasonably possible to solve this equation algebraically
$6\sin x\tan x-18\tan x+12\sin x=3$
kheerii
it is what is written
yeah this doesn't seem doable
in problems like this we normally find either x or sin(x) or something
but for this problem in particular sin(x) ends up only be expressible in an irreducible quartic
which… although it technically has an algebraic solution, it is essentially the same as being unsolvable
shall i do from here?
whats the question tho
the question’s been posted twice what do you mean?
from here
and restated here
@fossil dagger Has your question been resolved?
still doing
i think i got it
i got smth so damn weird
@granite torrent @hallow walrus
check it once
check what
that’s not solved
Ah, okay
our point is that this can’t be solved using normal algebraic methods
maybe
what do you mean “maybe” that’s a fact
probably yeah
but im still gon try it to waste my time
ive got an idiotic answer
sinx - 3 = cos x
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everything in that table looks right
why do people delete pings... at least edit message to say smth like "disregard this msg"
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Could someone suggest me some research work that has a practical part? It is a very important topic that I have to have chosen tomorrow but at the moment I can't think of anything that interests me.
@dull mauve Has your question been resolved?
<@&286206848099549185>
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Do you have a question or ?
wtf
Close the channel if you don't need any help, or it will be considered as trolling and I'll have to ping the mods.
@hazy sand
@hazy sand Has your question been resolved?
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I’ve been researching the FFT, and during its derivation I came across the attached equation. How do those exponents add to get to that? Thanks!
c(2k+1) = c2k + c
so
e^(c(2k+1)) = e^(c2k + c) = e^(c2k) e^c
apply this with c = -2pi j m/N
you're just using the property e^(a+b) = e^a e^b
Oh, I think my intuition thought you could combine the C terms, but I see now that you can’t
Thanks!
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If v = 5/(4+s) and s(0)=5. How do I know the distance (s) at t=6?
I was wondering why stating ds = vdt doesn't work????
I noticed you have to calculate dt = 1/v*ds. Seems logical if you look at it, but why is the other way not possible?
Well seeing that ds/dt is v, how do you mean doesn't work? and how do you mean dt = 1/v*dt?
The latter doesn't seem right, the former does 
Well if you intergrate the first one you get s = vt =5t/(4+s). This doesn't give the correct answer.
Wait, there was a typo in the second one. Now fixed.
Remember that v is not constant, and is a function of t, so you don't get vt from integrating
V isn't a function of t, right??? I see no t in it? So why don't you get s =vt ?
In any case, you're basically working with $\dv{s}{t} = \frac5{4 + s}$, which you can e.g. separate
@devout valley
It is, assuming you're using v for velocity and s for position/displacement
Yes, but why is that.
Like I know integrals, and use them a lot, but I'm not really sure if I fully understand them.
For example, if you just have the mathematical integral of xydz, it would give xyz right? As it's not depended on z?
Like that's how I know it?
Well if you're assuming that x and y don't depend on z, that would be right, but if they did, it wouldn't be
But in the original formula, yes v is depended on s. But how do you make up that v is depended on t?
Here remember that s, the position, is a function of time (notice how they tell you that s(0) = 5, meaning that when t = 0, s = 5), and that v is the derivative of s with respect to t (so is a function of t)
v depends on s, which depends on t (and as per before, v is the derivative of s with respect to t)
Ahja I see it now.
So basically, within dynamics you always have to pay extra attention to what is depended on oneanother? And in this case with speed, velocity and distance, it always is depended on eachother, so you have to make sure to seperate the terms? Am I correct? 
Well you know how e.g. each of those terms are defined (velocity derivative of position wrt time, speed absolute value of velocity) at least
How do you mean separate?
Yeah what you sent here. You get the function with s together with ds.
Like always group them together.
Think I got it. Cheers for your help.
.close
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I'm lost as to why my answer to this question was marked wrong
show exact question, input and error msg.
i think it may be some kind of input error, or maybe they're expecting some format you're not complying with.
The exact question is the indefinite integral at the top of the image... there is no error message, other than my answer at the bottom was marked Incorrect
screenshot the whole thing.
we MUST rule this out before the math is called into question.
this is absolute and inviolable.
Unfortunately the window had to be closed; it's a simple question provided for our online proctoring setup verification, and since it's a mock test, we're only told "Correct" or "Incorrect" with no explanation
well
Yeah
your answer appeared correct
but now it seems it's impossible to diagnose what went wrong
Ever used Knewton Alpha? I hate it.
It's the online... "textbook" and "homework" my college requires us to use for all of our Calc II assignments
I'll sometimes use integral-calculator.com to check my work, and it's giving me weird results
So... I understand what it's trying to do, with u substitution... but the problem is that (5x^2 - 5)^2 at the bottom...
If we FOIL that out, it's 25x^4 - 50x^2 + 25
Also, it takes the derivative of (5x^2 - 5), 10x, but never seems to do anything with it...
Is this just a rogue answer?
bump
bump
<@&286206848099549185> Any other ideas?
Afternoon
Hello
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Can anybody help me with this problem?
I found it 1
Math community do not have any helpers at this difficulty I guess lol
I mean its easy tho
@sweet jungle Has your question been resolved?
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anyone here know hypothesis testing?
@viscid epoch Has your question been resolved?
not yet
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Someone please help I don’t know how this is wrong I cannot see it
<@&286206848099549185> I gotta turn this in by 00:00 EST 😭
I’ve been at it since like 8
are you sure the first quartile is 10?
If the median is 12 then yea(?)
3 on both sides, right?
I don’t know when to do the finding of the true value thing
Im guessing you’re implying I do that?
the first quartile is the median of all the data before the median yes?
Yes
how many data do you have before the median
6
and since its 6 we find the average of the 3rd and 4th data
so when we have even numbers we find the true value ??
idk what you mean by true value
Find average of 3rd n 4th
Add them then divide
thats your q1
6 and 10
yeah
@bronze forum Has your question been resolved?
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Not even sure where to start, and can't find any answers online. We've never dealt with problems with multple variables like this.
the answer is not 2 by the way, that is unrelated
Ima read over this question one sec.
thank you so much
d-ax.
that is the correct answer
when dealing with limits at infinity we are dealing with horizontal asumptotes
Here is my work.
let me look it over. thank you so much
Np.
I'll break it down to you, so when dealing with horizontal asymptotes at infinity there are 3 cases we must consider
ax^n/bx^c, if c > n then y = 0
If ax^n/bx^c, if c = n then y = a/b
ax^n/bx^c, if n > c then there is no horizontal asymptote
Now when you observe what I did where I negative bx +c as well as + d, the reason we can do that is because at infinity their impact will be so minuet that we can negate it. It has virtually no impact.
yes. that makes sense
I'm having trouble understanding where you go after getting sqrt(a)/a=2
Here I'll show yah one sec.
thank you so so much
Since x is approaching negative infinity we have to keep that in mind, thus when we break the absolute value we have to multiply the x by a negative.
Does it make sense now?
what confuses you?
sqrt(a) - 2a = 0, we can algebraically factor that.
are you confused as to how I factored it, how I obtained the root?
nooo okay
so once you solve for a then it gives you the 1/4?
what about the other favtor?
0, right?
i'm sorry.
Why are you sorry? Don't be sorry lol. Ur here to learn.
n is a real number and m just represents a variable.
how does that relate though?
Well it seems you were confused as to how we got the two solutions, so I was clarifying that.
Or r u confused on why we negate the a = 0
no, i'm just confused why the only solution is 1/4, instead of both 1/4 and 0.
because if a was 0 then ax^2 would be 0 and a would be -ax would be 0 so we would have lim x --> -infinity sqrt(bx + c)/d.
ima show
why that wouldn't work
thank you
lol.
it wouldn't equal two if we plugged it back in.
plus we would have a negative square root which is impossible lol, this is completely meaningless.
thank you 🙂
Yeah.
No worries. Any other questions u wanna clarify?
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ight gl to u. pce.
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I was wondering if someone could explain the logic behind bournoulli's differential eqn?
The method to be precise
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Can someone check if what I am doing is right?
this seems like a weird way to do this problem
why not just use a standard geometric series?
Standard?
jan Niku
I
yea i think this makes sense
I have never seen that symbol in my life 💀
OHHH
jan Niku
something like this
Mhm
you just need to adjust the numbers to fit the problem
I see
these are nice because theyre very standard and its just known that $$S_n = \sum _{k=0}^n ar^k = \frac{a(1-r^{n+1})}{1-r}$$
jan Niku
am i going completely out of the material youve seen in class 
oh
i see

well its almost right
but i really should have recognized that, sorry
i think you have an $n$ in the bottom, where you should have an $r$?
jan Niku
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Hi, stuck here not sure what I did wrong to get - n/3 instead of + n/6
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unsure on where to start with this one
i know what associative and commutative mean but without knowing what the star operation does im stuck
You don't need to know what the operation does. Just start on the left handed side and apply those two properties to "move symbols around".
that's not a star, that's a diamond.
but also yeah the point is you don't need to know its inner workings
you just need to push symbols around and explain in detail how each step happens
@violet verge Has your question been resolved?
not sure what you mean by push symbols around
Do you remember the definitions of commutativity and associativity? Basically applying those
@violet verge Has your question been resolved?
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Find the inverse to: $y = x^2+4x+5$
Merineth
How do i find the inverse when i have more than one x?
Because if i had only one x i'd just solve for it but
Are you sure that's the only information you were given
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Complete square?
wdym complete square?
No way wrong
oh
You still have to find the inverse by representing x in terms of y
Merineth
that'll be i-2 lol
$y = x^2+4x+5 \
y = (x+2)^2 +1 \
y - 1 = (x+2)^2 \
\sqrt{(y-1)} = x+2 \
x = \sqrt{(y-1)} -2$
Merineth
x^2 = a, x = +-sqrt(a)
where x >= -2
you sure of the direction?
Ok so you know x+2 >= 0
So you line 4, when you pick between +sqrt(y-1) and -sqrt(y-1), you can pick the positive one
ooh i see what you mean
I though it'd be fine to keep it in sqrt form
$y-1 = (x+2)^2$ I take sqrt on both sides
Merineth
Sorry im new to channel
You can, and the equation would still be valid, but you would be throwing away half of the solution space
When you have a = b^2, you always need to consider both a = sqrt(b) and a = -sqrt(b)
If you then know that a >= 0, you can just pick sqrt(b)
If you know that a <= 0, you can pick the other one, -sqrt(b)
If you don't have that information, then you can't pick, you just keep both (can write it as +-sqrt(b))
Can i even disregard in my case?
considering i have
x >= -2
i disregard the - right?
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Somehow I cant getting from the first thing to the second thing?
!xy
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
what's the other side of the equality?
okay
but what's the other side of this inequality?
....= sum....
it's cut off
Sorry this
oh I see
combine the two summations
ah wait let me think about this
Ofcourse
well
take one of the terms to the other side for convenience
$(1+x+\frac{x^2}{2}+\frac{x^3}{6}...)\sum_{n=0}^{\infty} a_nx^n=\sum_{n=0}^{\infty} a_{n+2}(n+2)(n+1)x^n$
kheerii
how can you create an x^0 (i.e constant term) on the LHS?
only by 1 times a0 x^0
ohh you are a big brain
Sorry, I dont get it
oh wait you weren't OP lmfao
well, how can you create a constant term on the left?
i tricked you
if x=0?
no.
n=0
both sides of this equation are polynomials
we aren't inputting any value of x
yes, but which term will it multiply with?
as in, we have 1+x+x^2/2...
a0?
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hi

can someone helps
ask your question if anyone knows the answer, they will help
I'm not too sure, sorry
of what?
of how to solve it I have some ideas but the steps will be very long
ok np
there is not really an easy way to do this problem algebraically and completely
i would just plug in integers until finding a solution
thats not professional
i have gave it to my teacher and he started laggin lol
i mean the true solution involves solving a quartic
and that's not very pleasant
if you want to be slightly more rigorous about it, you can notice that these two equations both describe half of a quadratic, therefore they have 1 real solution at maximum
then all you need to do is find that 1 solution and you are done (and this is best accomplished by assuming that x and y are both integers)
the problem is how to find that solution
i mean
@thick hedge where are u?
a more reasonable algebraic solution might look like this, but it's really pointless
rewrite x in terms of y in 1 equation, substitute into other equation, continually rearrange and square both sides until you are left with a polynomial
(this polynomial is a quartic)
depress the polynomial to make it easier to work with
apply rational root theorem to find any potential roots
would that even work?
why would it not?
i'm telling you that this problem does not have a clean solve solution
it's just "wow math"... for people to put on youtube thumbnails and get views because it looks hard
this is not a thumbnail
i was making an analogy/exaggerated statement
aha sorry my english is not so good
oh no worries
if you still are looking for a satisfactory answer, you can probably search for this problem online and read through the results
(most solutions have to assume x and y are integers... or at the very least, rational... though)
because if you don't assume x and y are integers or rational, this problem becomes very very unpleasant
so what is your advice to somone that want be good with equations?
at a school level or a math competition level?
asking because those two goals have very different pathways to achieve
a math competiton level
hm i see
we dont see so much in school level
that's reasonable
i'm not sure how good of an answer i can provide so i'll just say what ideas i have
i think the biggest way people start to improve at first is to simply go through a bunch of competitive mathematics problems
these can be accessed in many online archives... most competitions have problem archives, and AoPS has problem lists for AMC/AIME
for every problem someone get wrong, they go through the solution and try to understand two things:
- how the solution actually works
- how they could have come up with the solution on my own without any assistance/help
over time, i think doing this helps you see common tricks that are used in problem manipulation, and you slowly improve as you learn more
also, being surrounded by other math-talented individuals usually helps people learn due to motivational factors (if real life doesn't work, then finding a problem-solving discord might help)
there also exist many books that people use to learn (but personally i think some of these are annoying)
overall, i'm not really sure how to describe it as the process is usually really slow for most people, but it might help give you an idea
oh thank you so much for your time
welcome
you could ask this question to 100 people and they would all give you a different answer but i think everyone's first experience has involved these factors before
i appreciate your help you are good personne and again thank you
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its correctly understood that to show that a matrix is surjective (in terms of linear transformations) i either need to show that the co-domain is equal to the rank of the RREF matrix or that the RREF matrix only has leading one's?
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$someone knows sicence naturell$?
brahim3579
this is not how you're supposed to use dollars for the bot.
$sorry an=pi/{n+3}^n$
brahim3579
dollars mark the start and end of mathematical formulas
how
and the formulas themselves are written in a markup language called LaTeX
see pinned messages in #latex-help
Ann
where can i learn it
#latex-help has a cheat sheet, otherwise google "LaTeX typesetting tutorial"
anyway,
is this sequence part of a problem/exercise/question that you're doing rn and want help with?
go to #latex-help and click here to see pinned messages it has some resources to learn LaTeX. Overleaf has many articles on it, and there are books on it as well if you prefer
aha thanks
when you guys use it i think << damn how ,this guys are hackers>>
#bots and #latex-testing
for that
i mean i personally have several years of experience with it
but it is not... terribly hard to learn i dont think?
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with this how am i supposed to express the solution?
@balmy coral Has your question been resolved?
<@&286206848099549185>
,w rref [[1,0,1,2,1], [1,1,0,1,1],[2,0,1,1,1],[1,0,1,1,1]]
Interesting they say “multiple” 
Otherwise you could have what you have, or that the solution is (0,1,1,0) (note that your work shows x3 to be 1)
yeah i wrote on my paper x3 = 1
how do i express the multiple solutions then
with like t*(0,1,1,0) or osmething
There’s only one solution to this, you don’t have a line of them from this equation (if I’ve copied it right) as you have no free variables left
You’d e.g. want the rref to have zero rows (and no “0=1” ones while we’re at it)
Just (0,1,1,0) by itself is the solution you have here
yeah i would have wrote (0,1,1,0) just seems odd the exam paper stats "mutiple"
nvm it seems i dont speak my own languag properly
its means all solutions, which i suppose is just the one we've found
while we are at it, what do i do if lets say s=1
you mean simultaneous?
no, it just means all i guess
i just didnt think that word meant all but i asked around and it does
Yea “all” solutions sounds more reasonable I would think, probs what they intended i guess(?)
Isn’t that basically what you’ve done? Not sure I get the question?
sorry
i meant if s = s
like just any varaible
find for every s in the real numbers, how many solutions
in the last row it has two s's in, so at some points it will say like s-2 = s-1 and if s=2 then it has no solutions, right?
so for s not equal to two, i should just do guass and find some solution set
Yeah basically like that: choose different values of s, like if s=1 you get a solution but otherwise you won’t
which means i get a solutions one solutions for all numbers other than 2?
Actually wait a moment, I’m being slow 
But basically it’s kinda like that, choose different values of s, you may get e.g. no solutions or infinitely many etc etc based on where you get to
$$[
\begin{align*}
x_1 &= 1 \
x_2 &= \frac{s-1}{s-2} \
x_3 &= \frac{-2s+1}{s-2} \
x_4 &= \frac{s-1}{s-2} \
(1)
\end{align*}
]
$$
akiyama
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
$
[
s \neq 2
]
$
akiyama
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reaction for more information.
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With $s\neq 2$
@devout valley
The bot doesn’t render tex if there’s spaces
That would be a unique solution if you have that, as s is fixed in value
yeah, so since s = s we have either one solution with s =/ 2 and no solution with s = 2
Yep 
@balmy coral Has your question been resolved?
Didn’t even notice the capri sun 
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note that you have a zero row
that indicates that your transformation isn't full rank, so your vectors don't span
also, you can see that the second vector is a multiple of the first, so they can't be LI
so you effectively only have 2 vectors there, which can't span R3
the rank is the dimension of the column space of the matrix
(the space formed by using the columns as basis vectors)
also the augmented part isn't really relevant
you only need the rref of the matrix made from the vectors you're checking
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how do u know that the moment caused by f3x is counterclockwise and not clockwise
it doesn't really matter how you see these forces and if its counterclockwise or clockwise you just have to choose one and then stick to that
is C the point of rotation for f3x?
idk tbh
so for every point of rotation (I assume C,D and E), you calculate the negative and positive signs (by convention like this) around your point of rotation
Which value are you referring to?
The red one, right?
Yeah
That's not the moment of F3
It's CCW because of the line of action
Line of action at point A is here
So the Moment of F3x would go CCW
Like this
@wicked frost
idk I would still think it would be cw
idk how to explain it, it just looks like it would be cw
You can think it all you want, it goes CCW, because of the reference for point A
Do you see the line of reference for Point A, the green line I drew in? Do you see how it would go CCW around that line?
I still don't see it
is there like another way of doing it rather than just by looking at it and trying to tell the direction?
ye
See how F3, is under that line?
ye
F3x goes to the right, and that line is the reference point
Notice how the F3x would rotate CCW, around that line
If you still don't see it, I suggest asking your teacher, for help, but they are probably going to say something similar as that's how you determine direction
it might help if you draw a line from A over to the base of F3x, and notice that F3x is counterclockwise from that line
A similar way is shift that reference point, that you are focused on, down the beam, horizontally, to each force. If you shift point A along the line so it's in line with F3, you can see that F3x is CCW
if a force were pulling directly along the purple line, it would just be pulling away from the pivot and not contribute in either direction, but F3x is above that line; that is, it has some component that is CCW relative to the point it is pulling from
@wicked frost Has your question been resolved?
Yeah this makes sense thanks
Does this method always work for any moment?
yes
Tysm
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Can someone tell me what did I do wrong? Why do I get a negative answer? I need to find the surface created by rotating the function along the OY axis
@lethal moss Has your question been resolved?
You should integrate from t=0 to t=π/2
why? isn't the integral before the change from 0 to a?
But the integral is with respect to t, not x. You are not changing the variable
Also, when finding the area or the volume of something you must always integrate in positive order (that is, if t ∈ [a,b], then t varies from a to b, and not from b to a), otherwise you obtain the same number but negative
And be careful, x goes from -a to a, not from 0 to a
Yeah this makes sense
Thnx
Could you help me with something else? Is another integral but it's kinda different
Yes
I just don't know how to do this.
I need to find the volume of the body formed by rotating y^2=2px around y=-p, limited by x=p/2
Like if it was rotating around y=0 then I would know how to do this but I dont know how to do it around y=-p
Well, let z = y+p
Then you are just rotating around z=0
And you just applied a translation, so the shape, the area and the volume did not change
Rewrite y^2=2px in terms of z and do as usual
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Can someone please explain what happened here
How did the a become 0-1
on your photo i guess youve started to cope with Laurent series?
if so, then analyse this:
Im doing z transform
ok then )
I believe they used the formula of S infinity
But the first term in this case shouldve been aZ
on yoru phot, there has been sued geomtetric series,
and its sum
$\sum_{n=0}^{\infty}z^{n}=\frac{1}{1-z}\text{ }\text{ where }\text{ }\left| z \right|<1$
Yes
S = a/(1-r)
Joanna Angel
Thats true for the first part
the second series wud look liek this:
$\sum_{n=0}^{\infty}\frac{1}{z^{n}}=\frac{1}{1-\frac{1}{z}}\text{ }\text{ where }\text{ }\left| \frac{1}{z} \right|<1$
Joanna Angel
You can just set $m = -n$ so that $$\sum_{n=-\infty}^{-1} (a^{-1}z^{-1})^{n} = -1 + \sum_{m=0}^{\infty} (az)^{m}$$
yes that works like:
$\sum_{n=-\infty}^{-1}z^{n}=\sum_{n=1}^{\infty}z^{-n}=\sum_{n=1}^{\infty}\frac{1}{z^{n}}=\frac{1}{z-1}$
Joanna Angel
ofc
JessicaK
How did you separate out this -1?
and then how did you change the limit?
$\sum_{n=-\infty}^{-1}\left(a^{-1}z^{-1}\right)^n=\left(a^{-1}z^{-1}\right)^{-1}+\left(a^{-1}z^{-1}\right)^{-2}+\dots$
Then apply the rule $\left(a^{-1}z^{-1}\right)^{-n}=(az)^n$ to obtain $(az)^1+(az)^2+\dots$, which is $\sum_{n=1}^\infty (az)^n$
d
Then, the sum from n=1 to infinity, is the same as the sum from zero, but subtracting the term with n=0, which is (az)^0=1
@plush plaza Has your question been resolved?
Oh thankss
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is
j💫
a exponential function
Or does the + 3 make it not one
Asking bc i wanna check my answer
Pls Lmk if i missed one
I thought exponential is $a^x$
Zemitrix
I learned exponential function is always in the form $a \cdot b^x$
j💫
they're essentially the same thing
Why you didn't choose 5 one
First is indeed correct
So the first option is an exponential function?
Oh is that one? i got confused bc the exponent was inside the square root
Yrah
I guess yes lemme check graph
Ig it's exponential
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can someone help with this
im not even sure wha it's asking me to prove
for (c)
if x = a then (x - a) = 0 and 0 * any function = 0
and if f(x) is a nth degree polynomial then h(x) is n-1th degree polynomial by definition (and also by what was proved in part (a))
and we don't actually care at all about what's in that h(x)
other than that it's 4th degree
so what do I prove?
@delicate ore Has your question been resolved?
@delicate ore Has your question been resolved?
For (c), you just apply (a) to p(x). Then substitute x-a to x to get back to f(x), and use (b) to say that g(x+a) is a polynomial of degree n-1.
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This question is related to Calculus 3 and more specifically Triple Integrals. I want to know how I can set up the integral when a sphere is shifted.
The question is:
An object is defined by eqn x^2 + y^2 + (z-1)^2 = 1 in the first octant. How do I find volume? I have tried spherical and cylindrical coordianates and both lead to nighmare integrals.
@signal shell Has your question been resolved?
<@&286206848099549185> If anyone wants to do some multivariable calculus...
nope
have you tried parameterizing the curves of the sphere?
Show ur work
Or im@not helping u
1sec
I refuse to help you actually if you don’t show ur work
Sorry it's quite a mess
I started off with cylindrical, moved to spherical and then jumped back and forth..
Please ignore page 92, I was trying to relate it to another problem
Hello! Have you tried first drawing a sketch of the surface? 🤔
Hi! Yes I tried. I know its a sphere thats shifted up by 1 on the z-axis. I also confirmed it by using an online tool.
Because its shifted up by one, the Phi is not a constant and that is what is stumping me.
Ok I think cylindrical would be the easiest way 🤔, if you want to solve it with triple integrals and with the given surface
I tried using cylindrical, cutting the sphere into half and making it like a bowl by adding an imaginary plane at z = 1. I was thinking of then doubling it to get total volume.
But it leads to a very weird integral
Wait how are you getting those bounds for z
From this eqn, you get 2 functions for z, roof and floor surfaces. Just put those as the bounds of z
z > 0 and z < sqrt(1-x^2-y^2) + 1?
Yes
Think of when you want yo find the functions that form a circle x²+y² = 1
y = √(1-x²)
y = -√(1-x²)
It's kind of the same algebra
Find those 2 functions for z, then use them as the bounds for z
z > 1-√(...)
Sorry about the typo
Ok dw
I would then sub the x^2 + y^2 with r right?
r²
Ok
dude it says first octant
since you cannot take negative
we dont have to actually go for 2. part
sorry for interrupting by the way
Dw
The surface is completely above the xy plane 🤔
Since it's a sphere with radius 1, z-1 goes from -1 to 1, so z goes from 0 to 2
Is that what you mean (?
Set the triple integral with this bounds for z and the ones you already calculated for r and theta. Then the integral is kind of nice
You're right about kind of. There is a sqrt(1-x^2) integral and I despise those lol.
But yes, it gives me some semblance of an answer
Thank you so much!
I am getting the answer that was given.
Ok great 👍🏼
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This is a right parallelepiped 80 20 and 5 how do i find the hight
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plot one line at a time as a function of t and see where it goes wrong
or just use wolfram to simplify
,w simplify (3t^2-3)^2 + (3t^2+3)^2 + 36t^2
hmm its the same as what I got
then I divided everything by 18 or can I not do that since its in a root?
18 is under the square root
ah I see now
I should've factored out an 18
then taken the square root of 18
right?
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I did the question but why is 15 not a solution?
is this a case of mixing up radians and degrees maybe? the problem is using radians and you seem to be using degrees
hm
ill try it radians again rq
nah radians doesnt work
I get 0.7853 smthing
which is def not
plus I got 135 which was one of the solutions so
x/3 = 45
x = 45*3
no?
💀
right you were multiplying both sides by 3 and you divided 45 by 3 instead of multiplying
nvm I kept dividing 45 by 3 😭
bye
so 3pi/4 and -pi/4 should be solutions in radians
nah
x/3 is there
you have to solve for x
not x/3
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teacher's key
yeah there's a way
Replace x to (x-1)/2 both sides
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How do I do this?
do u know how to find f(3+h) and f(3)?
F(3) is just 3^3 right
yea
And f(3+h) = (3+h)^3?
yeah and now use those values in the expression
Oh so u get like
27h+9h^2 + h^3 / h
And then u can factor that into
27 + 9h + h^2 right
(a + b)^3 = a^3 + 3a^2b + 3ab^2 + b^3
Yeah but then we also have a^3 -a^3 right
Cause -f(3)
oh u simplified it
yeah and thats simplified
Alright thanks
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find the largest rectangle that can be inscribed under the curve y = e^-x2 in the first and second quadrants
Imagine the height of the rectangle is the y coordinate and the width of the rectangle is the x coordinate
umm
These types of problems are done usually with symmetric curves
So you can make a formula for half of the rectangle by doing
x*y
Then you can do 2*(xy)
Yea cause x is the width
