#help-36
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im using it on F(x,y)?
I was literally getting ready to leave for work tho lol 
Me too 
it will
vvv
You should expand this and compare
to this
ok weird notation actually
but i mean like compare theirs to your expansion and the left overs should vanish by lagrange
but i dont know how they converted everything to matrix form
the idea is instead of trying to get their form, you expand their thing and show if you subtract this from your result it's 0
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I need help please
with what?
Don't we all
Asking the actual question right away is more likely to get responses.
Asking "Can I ask...?" or "Does anyone know about...?" doesn't give people enough information to decide whether they can help, and answering can feel like a promise to help with the actual question, which they might find themselves unable to.
Polynomial division
I don't know long division BTW but I am willing to learn it by force a
what is the problem?
have u got a specific question?
Well you should learn long division first
Polynomial division is long division generalized to algebraic expressions
you divide variables instead of numbers
Can you teach me tho
Khan academy basically covers all of this
is this even divisible lol
Seriously
Yea i took that lesson b4
OK I'll go watch it
This environment is suitable more for direct questions, not teaching whole concepts, as that takes a large amount of time. Maybe somebody has the time right now. I don't, sorry.
Ok
In algebra, polynomial long division is an algorithm for dividing a polynomial by another polynomial of the same or lower degree, a generalized version of the familiar arithmetic technique called long division. It can be done easily by hand, because it separates an otherwise complex division problem into smaller ones. Polynomial long division i...
Thanks
np
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and here too <@&268886789983436800>
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Can someone help me find the coefficients for 5. I have that the integral is equal to
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yeah confused again on the meaning of the problem
like, are there any orders for the bulldozers? does A and B have tk be adjacent to sweep? and for the orders, is it like for some ordering of the movements of the bulldozer, there would always be one left over? or whatever ordering it is, a specific town will be left over?
my reading comprehension is maybe just ass idk
@jagged flare Has your question been resolved?
Regarding your first question:
In general you shouldn't assume something if it isn't explicitly said. So the towns don't need to be adjacent for sweeping (you can also infer this from what they have asked you to prove).
And regarding your other question, it's definitely the case that you have to show it for any ordering, because there obviously exists some ordering in which exactly one town cannot be sweeped away by the rest. (Put the bulldozers in descending order from left to right..)
mm
for diffrent orderings (like left to right and right to left), the unsweepable town can be diffrent right?
Yeah
The way they have written the question is:
You are given some ordering of towns, there is exactly one which is unsweepable
This is the same as:
Prove that for any ordering of towns, there exists exactly one town which is unsweepable
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ok ty
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is p and r labled correctly???? because i dont get how this makes sense
because the bearign of p (plane) should be 78
however the bearign of the resultant is 78 instead
<@&268886789983436800>
@orchid scroll Has your question been resolved?
mb ir ead the qeution wrogn
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is 0 a natural number?
depends
some ppl say yes, some say no, it's up to definition
but it's a natural number i dont care
bruh i thought math can always be definied
but haseeb never said math can't be defined. it's just that some people work with different definitions.
i guess the question is, what's convenient/makes sense?
for most things, there is only one definition that makes sense, but sometimes its more convenient to include zero and sometimes to exclude it
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0 isnt positive or negative though
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✅ Original question: #help-36 message
or it's both positive and negative, depending on your definition
but that's not really relevant to your question
adding a zero to a number wont move move the number to the right or left on a scale
sure
so what
what would a catholic say
they'd defer to the Pope
is zero a natural or a whole number
"whole number" isn't really a term used much in highery level math because it's unclear what it shouls mean
its positive and negative numbers actually
without pi, fractions or square roots
or powers
PURE number
you're probably looking for the term integer.
but whether 0 is positive is based on convention
as i said
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Renato
|{segments connecting 2 vertices}|-|{edges}|=|{diagonals}|
You count the segments connecting 2 vertices, then minus n (which is the number of sides)
or just count it directly like a diagonal need 2 points, so u have n points to choose for point A, then you have (n-3) choices for point B because point B must differ from point A and the two next to point A, then divide by 2 because the order doesnt matter ( AB same as BA )
Yeah that too
I put it the other way because I assumed the OP just learned about combinations
So the number of "segments connecting 2 vertices" is easier to calculate
n choose 2 - n
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yo how do I do this i've got no clue
@late gazelle Has your question been resolved?
The question says you need to find the sum of these two lines
Why 3d
there is elevation
But there's no depth
map coordinates describe x and y, and z describes the change in height
Oh damn you're right I skimmed that part
@late gazelle
here is your hint to get going: your first hilltop can be described with $\mat{500 \ 700 \ 400}$ in metres. Likewise, the second hilltop is at $\mat{800 \ 350 \ 320}$
calculate the displacement vector, the difference of the two, and the straight-line distance between the two
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✅ Original question: #help-36 message
sorry, i had to go for a few minutes
alright lemme see what i can do
so thats distance between the two mountains right
oh wait i made a slight mistake
i forgot the height
d=468m roughly
where do i go from here
i cant really say the "slack" is halfway along can I ?
yeah right
its an isosceles
each equal side is cable length / 2
so i can, nice
so like 234 meters ish then
and the "slack" is $= \frac{5}{100} 468$ ?
KB
wait but like
you are kinda done lol
cable length is 468 and slack is what u wrote
oh slack is what we were finding
i thought it was the cable length including slack
so the two similar lines
oh if that's all i needed that wasn't as bad as what i thought
yeah
or is it just 8+2-3
yes
oh so we omit the i, j, k then
$\mathbf{a}\cdot\mathbf{b} = \sum_{i}a_ib_i\$
$\mathbf{a} = \begin{bmatrix} a_1\a_2\a_3\\dots\end{bmatrix}$
$\mathbf{b} = \begin{bmatrix} b_1\b_2\b_3\\dots\end{bmatrix}$
Flash09A14m
dot product is <x,y,z> • <l,m,n> = xl+ym+zn, which is a scalar
multiply each is, js, ks together and sum them up
dot product returns the projection of one vector onto another
yea ik what it is and how to do it but we haven't used i, j, k notation yet so i got confused
Scaled* projection
and its also 3d now
i, j, k represent the unit vectors for each direction
i, j, k are unit vectors of the x, y, z coordinates respectively
i understand it but not in calculations
if you understand it now then ggs
The projection is scaled
I like to call it the "effect" of the projection
Pure projection of a onto b would be a dot b divided by |b|
Yes
so $a \cdot b = |a||b|\cos(\theta)$
KB
yeah
,w 40 cos(50
does wolfram auto does trigonometric functions in degrees
for this would $\theta=\arccos(\frac{\overrightarrow u \cdot \overrightarrow v}{|u||v|})$
KB
ye
look at the cosine graph and see when cos theta = 0 and most of the time bind yourself to 0 to 360 or 0 to 2pi (in radians)
that should tell you that arccos(0) = 90 or pi/2
what is this ew
Length Qsn
projection was my #1 opp last year when doing 2d vectors
use this
anytime you see 'projection' in a problem, it wants you to dot product
if you want to add a+c, just add the ijk together
hmm i remember it having unit vectors tho no? or was that something else
yeah
This would give you the mag
for the vector form,
You need to apply
(a . b / (|b|^2) ) * b
this is a method to find the projection of vector a onto vector b
can proj be negative?
as in?
bc i got $\frac{-18}{\sqrt{30}}$
KB
if you take the positive value for this you would get the magnitude of the projection of vector a+b on c
But the question isnt asking you the magnitude
doesn't projection give me another vector
ahhh
this is how you calc the projection vector
what you found was the magintude of the projection
is $\proj_(a+b){c} = \frac{(a+b) \cdot c}{|c|}$
KB
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for magnitude ?
as in take absolute value of this
magnitude cant be negative!
sooooooo. Projection of a on b is $= |\frac{a\cdot b}{|b|}| b hat$
KB
b hat b ^ thingy
unit vector of b
ah interesting
wait
wheres the minus sign
you remove the minus sign if you are calcing the magnitude
but you are finding the vector so minus sign is imp
so we do want the - now
i vaguely understand this but not entirely
ok nvm idk how to even start
okay, make a displacement vector v = xi + yj + zk
so |v|² = x²+y²+z²
then take v dotted with x unit vector (here, it's denoted as i), you get
v dot i = |v| * |i| * cos(alpha)
|I| is just 1
and then you repeat for the rest of the x y z for the displacement vector
and them simplify final answer to get the equation they got
Yes
The magnitude of the projection is a dot b divided by |b|
The actual vector would be that multiplied by the unit vector of b
uh huh
where x = cos^2(alpha) and so on?
|v|cos(alpha) = x
(|v|cos(alpha))² + y² + z² = |v|²
you are looking at the v projection on x axis
you'll end up with something like this
|v|cos(alpha) = x = |v| • i
|v|cos(beta) = y = |v| • j
|v|cos(gamma) = z = |v| • k
(|v|cos(alpha))² + (|v|cos(beta))² + (|v|sin(gamma))² = |v|²
and then you divide all size by |v|² to get
cos²(alpha) + cos²(beta) + cos²(gamma) = 1
we made a displacement vector v = xi + yj + zk
what's the magnitude of the displacement vector? |v| = ? @late gazelle
$\sqrt{(v_1)^2+(v_2)^2+(v_3)^2}$
KB
no
magnitude of a vector is not that?
$\sqrt{(x)^2+(y)^2+(z)^2}$
polar
oh same thing, v_1, v_2, v_3 are just the x, y, z components of v
yeah, and you know where i got those from right?
just by dotting the displacement vector V by i j k unit vectors
if x^2 = cos^2(alpha), x = cos(alpha)
yeah, and we got that because we took the displacement vector and we saw how much we projected through the x axis
and we did that with a dot product
so where/how does the |v| part come into this then?
|v| • i = x
x = |v||i|cos alpha
|i| = 1
x = |v| cos alpha
x² = |v|² cos² alpha
and that only holds equality to our original if |v|^2 is = 1 and if v = cos^2(alpha) + cos^2(beta) + cos^2(gamma) its equal to 1?
Okay, let me explain properly now that I'm on a computer.
The question wants us to show that cos^2 (alpha) + cos^2(beta) + cos^2(gamma) = 1 is true for any directional cosines of any line in 3D space.
Before, I begin, I'm going to introduce the notion of a unit vector.
A unit vector, often times denoted as **i j k** are vectors with a magnitude of one that point to the **x y z** axis on a 3D cartesian coordinate systems plane and are often used to describe direction of a vector.
Let's start off with the question. The question first wants to 'use' a displacement vector.
We can make a sample displacement vector by only considering the points P1 (0,0,0) and P2 (x,y,z)
We can use the idea of unit vectors to define direction to the displacement vector, and we can call this vector 'V'
V = (x-0)i + (y-0)j + (z-0)k = xi + yj + zk
So that we can perform a scalar product, we will find |V| which happens to be
|V| = sqrt(x^2 + y^2 + z^2)
Hopefully that makes sense so far, all we did was defined a displacement vector and took it's magnitude.
Now, since we know what the magnitude of the displacement vector is, we can now take the scalar product of it with respect to the i j k unit vectors. This will describe the 'projection' of the displacement vector on x y z, so basically it's contribution to the x, y, z coordinates.
So,
Using the formula u dotted v = |u||v|cos(theta)
|v| dotted i = |v||i|cos(alpha) = x
|v| dotted j = |v||j|cos(beta) = y
|v| dotted k = |v||k|cos(gamma) = z
Now, recall how I mentioned that unit vectors *are of magnitude 1?* (It's often good to know that whenever I say 'unit', I mean anything of value 1.) We can then say |i| = 1, |j| = 1 and |k| = 1
|v| dotted i = |v|cos(alpha) = x
|v| dotted j = |v|cos(beta) = y
|v| dotted k = |v|cos(gamma) = z
Now, from that, we can recall our displacement vector and square it to get
|v|^2 = x^2 + y^2 + z^2
Plug everything in
|v|^2 cos^2(alpha) + |v|^2 cos^2(beta) + |v|^2 cos^2(gamma) = |v|^2```
woah, this is gonna take a minute
Notice how |v|^2 is a common term in |v|^2 cos^2(alpha) + |v|^2 cos^2(beta) + |v|^2 cos^2(gamma) = |v|^2
We can divide the entire equation by |v|^2 which is mathematically sound and we get
cos^2 (alpha) + cos^2(beta) + cos^2(gamma) = 1
Which is what the queston wants.
that makes a lot more sense
Yeah, try the question out and see if you truly understood it - without any help
@surreal grove blessing us with a virus 🙏
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mmm, this sounds like the euler theorem for the diagonals of a polygon
Care to elaborate?
I'm sorry I cannot help that much here, I just wanted to tell you that it looks like that theorem😅
Does that say prove the number of diagonals of an n sides polygon is n(n-3)/2
ye
First, think about how many diagonals you can draw from 1 point
So if you're sitting at the vertex of a polygon, you can draw n lines to other vertices that aren't already sides of the polygon?
In particular, if you fix a vertex, how many vertices can you draw a line to that aren't already sides.
n-1
So is your guess of n-1 diagonals from a given vertex correct?
Yes. If you fix a vertex then you can't draw a line to any of the adjacent vertices, since that would just be a side of the polygon. You also can't draw a diagonal from the vertex to itself. That leaves n-3 vertices to draw a diagonal.
then wat
Now do the same for all points on the polygon
why / 2
Cause youre counting a diagonal twice, for example for the diagonal AC you counting from A to C and then again from C to A
i see because for it to be a diagonal two edges need to connect so we are double counting
ye
can u help me write the proof
You've pretty much got it served on a platter now.
I am not really sure how we got to the n - 3 formula
Go back and read what we talked about.
.
seems out of the blue
In what sense? If you draw the situation, as you should in pretty much any case, it's pretty clear both what I'm saying and why it's true.
yes but I was looking for an formal argument rather than a visual proof
It's a formal argument which you can convince yourself works using a visual aid.
It doesn't mean it's a visual proof.
what would be the formal argument be?
I still need help with the induction
It's formal enough in that a polygon is already a rather geometric object in nature.
Induction would work but this would require that a polygon in n vertices can be used to construct a polygon in n+1 vertices. It can, but this construction in itself would be geometric...
It should be a rather intuitive fact that from a given vertex you can draw n-3 diagonals. This is where the geometric intuition ends.
If you want to avoid this at all cost you can also compute the number of pairs of vertices, hence giving you the total number of lines you can draw between any two of the n vertices in the polygon.
Then you could subtract the number of such lines we know are not diagonal.
how do I do this?
Well you need to compute those two quantities.
How many pairs of vertices can you pick from the n vertices in the polygon?
How many lines in the polygon don't count as diagonals?
How many pairs of vertices can you pick from the n vertices in the polygon?
I dont know
Think about it. You spent less than a minute thinking about what I wrote before saying you don't know.
n - 1
Did you check n-1 fits with that number or did you write it down because it sounds nice?
Does it make sense that n-1 is the number of pairs of n vertices?
wdym by number of pairs of n vertices?
you mean the combinations of pairs of vertices?
The number of ways you can pick 2 vertices from n vertices.
for example if the edges of a triangle are 1 2 3
then I have (1,2) , (1,3), (2,3)
I dont think I understand, care to explain with other words?
How many ways can you select 2 people from a group of 5?
5 c 2
Ok. How many ways can you select 2 people from a group of n?
n c 2
So how many ways can you select 2 vertices from a set of n vertices?
n c 2
So there are nC2 possible lines you can draw between vertices in the polygon.
How many of them do not qualify as diagonals?
Out of all the lines between vertices.
There's a number of lines between vertices we don't count as diagonals.
What are those lines?
How many of them are there?
the adjacent edges
no?
Adjacent to what? We don't have a fixed vertex here.
If you think of a polygon with n sides with its diagonals drawn, what is the number of lines in the polygon that aren't diagonals?
If you try with a square (and its diagonals) first, it should be apparent what this number is and what those lines are.
If you think of a polygon with n sides with its diagonals drawn, what is the number of lines in the polygon that aren't diagonals?
the sides, n
@blissful meadow
Yes. So now we have nC2 pairs of vertices (and therefore lines between those), and we want to get rid of the n lines in there which aren't diagonals.
What's left?
what does n C 2 represent?
The number of pairs of vertices you can pick from amongst the n vertices of the polygon.
You can imagine that any such pair gives a line between two vertices.
You can imagine that any such pair gives a line between two vertices.
okay so nC2 lines.
we want to get rid of the n lines in there which aren't diagonals.
nC2 - n, got it
@blissful meadow
Yes, so now you can write down what nC2 means computed and combine those.
how?
care to elaborate?
nC2 is some expression.
,w simplify binomial(n, 2) - n
@blissful meadow
What?
n(n-3)/2
now can you help me prove it using induction? @blissful meadow \
Well, the first one was more like a visual representation, I wouldnt call it a proof since it was kind of non formal argument
I didnt realized until it was too late
however, the argument should be fairly similar, right?
first we use the base case n = 3, then assume it holds for n = k, and show that it holds for n = k + 1
Is this weak induction
ye of course
Why not use strong induction
strong iirc is used when the inductive hypothesis depends on other previous hypothesis
for example when you ahve a sequence an = a_{n-1} + a_{n-2} , if you assume P(n) then you are assuming P(n-1) and P(n-2), I think?
@blissful meadow
I see there is no need to find polys that have 4 or 5 sides but you only need a k side
Make senses
care to elaborate?
Base case is n=3 which is correct
Inductive step for k also good
I think for k+1 is basically add 1 more vertex, which is keep same number of diagonals for k vertices and add (k-2) vertices
Because this new vertex doesnt connect itself and the 2 vertices next to it
what
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. @proud raft
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I have a doubt .
9 different objects should be distributed to 7 different person .
Atleast one should be distributed. .no of ways is 8⁹-1 .
Why the most common explaination is take an empty box to avoid counting exact cases.
But I don't understand it .
Can anyone explain logically
Derive the formula mechanism wise why is this that .
Star
I really appreciate your help
People like u make the world a civil society
Thanks
i guess it is just to avoid casework, if i understood your question correctly?
like it would be nine different cases would it not
exactly 1 object was distributed, ...
I don't understand the reason
The formula has 8⁹
.the formula should have had 7⁹ because objects are only seven
@rugged merlin ???
Please don't ping individual helpers unprompted.
sorry i like
dont understand what that is saying
No problem
Anyone else that can help ?
Doubt closed
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this is also combinatorics
8^9-1 does not feel correct
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✅ Original question: #help-36 message
"The formula has..."
Can you cite your source on this? What formula?
Because conceptually I agree with Paradox, that this doesn't feel right
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Hijack
modping?
The length of the shortest path that begins at the point (-1, 1), touches the x-axis and then ends at a point on the parabola (x - y)^2 = 2(x + y - 4), is:
Mb wrong ping
Wait I've seen this ques...
It's from the black book-
Alr i was going to edit it but it pinged
True
That's a really good ques... I'd have loved to help u but I need to go right now...sorry
Alr no worries
What step are you on?
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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
@proper lion Has your question been resolved?
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This is college algebra rational equations. I already know to move all the numbers to one side, and to make a sign chart, but im not so confident on the details.
have you attempted this and gotten stuck? if not, since you have some idea, maybe try it first and we'll see what else needs brushing up on.
got it.
ok, i tried to solve it. Is the solution set (-∞, -5) U (4, ∞) ?
i put it to one side, then combined the equations, then tried to find what makes the numerator and denominator 0, then put those numbers into a number line with negative and positive infinity and tried to find what numbers make the solution negative or positive.
@brave moon Has your question been resolved?
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So with this question... does the sample size increasing affect the confidence interval?
Sorry for the ping
I feel bad about that now
I didn't realize I was pinging 1500 people
I would like some help tho
!15m
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i dont know what to do in here sorry
so you’re fine.
alright
Does anyone know about statistics?
I'll just have to come to this question later
I'm wasting a lot of time on it
could you send the entire question?
there’s context missing, like the meaning of the variable s
sorry about that
I just realized I made a mistake
I failed to consider the changed mean and SD in part 2(a)
I'll have to redo that
Nice
updated version
As if it'll make a difference to our answer in part 2(b)
I’m not familiar with statistics so I can’t really help, but have you tried looking up the relevant sections in the textbook/course materials where they mention confidence intervals?
@fresh pendant Has your question been resolved?
I'd have to dig through a fair amount of content
but it's achievable I suppose
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How do I do part b
notice that part of f'(x) is similar to g(x)
namely the xarcsinh(x^2) part
Yes yes
fill in the missing parts
integral F+G dx = integral F dx + integral G dx
it's like
forgot if whatever it was called FTC 1 or 2
So I can split the integrals apart? Do them separately and add them?
I'm so confused lol
you can split integrals appart that's part of the fundamental theorem of calc
Haha I can read it if I focus enough 😅
Tytyty
keep going w integrating
Kk I kinda gor stuck as well
I don't know I coukd integrate x³/(x⁴+1)½
substitution
u-sub
x^4+1=u
I see
wait if you didn't know about the adding thing how were you integrating things like x^2+x
I didn't think too much about it
I should've 😭
I'm still stuck😭
Inded did something wrong
Sorry for the messy working out
the derivative is not correct
recall power rule
no worries
Is this rightt
Ty😭
why -2?
no negative sign
Oh true kk
Kk im going to try working out the integral in the question with this
So when I solve it, am I supposed to get a constant value -1/4
Gtg so
Ty for all the helppp
<333
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Can someone explain why for $\int\frac{dx}{2+a\cos x}$ I can't say $a=\cos x$ and say $\frac{\arctan(\cos x)}{-\sin x}$ I see that it doesn't hold if I take the derivative. But I want to understand what is wrong with the sub
BigBen
The main issue is the x variable you are integrating with respect to
when you say let a = cos(x), you are trying to treat a part of the function as a constant while it is actually changing as x changes
instead you can do something like u = cos(x)
imagine instead of a it said 7
Ok so the issue is a is a constant that is between 0 and 1 and I set it equal to a function that is between 0 and 1
putting 7=cosx is obvious nonsense
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I am supposed to use continuous convolution on this function with itself (the second image is the given formula continuous convolution; I basically have to calculate (f * f)(x) )
I used it on f(x) which gives me an Integral over R with f(x-t) f(t) dt inside (notationally I use t here instead of x')
Now I have already established that t would need to be within [-1 , 1] for the integral not to be 0 (as the f(t) part of the integral would otherwise be 0 so that part is not of interest) and that since f(x-t) also needs to not be 0 only the area -1<=x-t<=1 is of interest as well
(Which I then summarized to t needing to be within [-1 , 1] and x needing to be in [-2 , 2] (which I got from the maximum and minimum of x-t) for the integral to not be 0)
Now I am stuck though since if I don't really know how to define over which parts to integrate to get the resulting convolution function (for which I think I at least already have (f*f)(x) = 0 if x∉[-2,2] ). Are the borders just -1 to 1?
Sorry if this is like a weirdly specific topic or something
@cedar lichen Has your question been resolved?
@cedar lichen Has your question been resolved?
The integral should be over all of R
But you could replace the bounds with -2 and 2 here
Since it's always zero outside of that
that is basically what I did but why -2 to 2 (I tried it with -1 to 1 )? Since I integrate over t wouldn't it be entirely 0 for any x bigger than 1 or smaller than -1?
Yeah -1 to 1 should work too
Just note that the function won't always not be 0 inside that interval, it depends on what x is
You have the integral of f(x-x')f(x') dx'
The f(x') precisely had support [-1,1] so you can factor it out if you set the bounds
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I am not really sure what to do next, or if this is complete or not. The question is: Suppose a,b,c are integers. If a|b and a|c then a|(b+c)
I am new to proofs, so sorry if the structure is off.
I have done this so far:
Proof. Suppose a|b and a|c, if b=ak and c=az, integers k,z
Then b+c = ak+az, so a|(b+c) if ak+az=aq, integer q...
...
Then b+c = ak+az = a(k+z), which is divisible by a
Ohh, that makes sense. Thank you!!
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why is there a dx term in the denominator?
in the second equation
when did that get introduced
nvm, i see
forced factor
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this might go a bit beyond the scope of the question, but how would I go about the actual transformation to the function g?
my original idea is that I could take that limit equation i have, and convert it back to cartesian coordinates
You mean how you would define g?
but I couldnt figure out how to get rid of cos^2 theta
i believe so
Because then it's just about "adding" in the point at (0,0) which isn't initially defined on f.
You can write it down piecewise.
is that with the polar equation?
also arent there issues with r being only positive despite the only restriction being xy != 0
I mean either would work, but there's nothing stopping you from defining g(x,y) = f(x,y) when (x,y) != 0 and g(0,0) = 0. This is continuous as you wrote.
Like $$g(x,y) =\begin{cases} \frac{7x^{2.5}}{x^2+y^2} & (x,y) \ne (0,0)\
0 & (x,y) = (0,0)\end{cases}$$ is just $f(x,y)$ with the hole "plugged" where it isn't defined.
Azyrashacorki
im realizing now that was the point of finding the limit in polar coordinates
so if my limit were say, DNE, then the mapping from f to g wouldnt be possible?
Yep
It's like how $f(x) = \frac{x(x+1)}{x+1}$ is just the line $y=x$ with a hole at $x=-1$. The limit exists so you could define $g(x) = x = \begin{cases} \frac{x(x+1)}{x+1} & x\ne -1 \ -1 & x=-1\end{cases}$
Azyrashacorki
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I need help, guys.
Rotate one minus by 90° then add to first - then u get +
but what
Well it depends on what structure you're proving this for. If it's for R, assume field axioms for R, and hint: you need to use that if $x \in \mathbb{R}$ then $x \cdot 0 = 0$ and $1+(-1)=0$
Annie Maqionde
Are geometrical proofs invalid?
yeah
thank you annie
do you think that you need to be very intelligent to get a math major
that's what I am trying to do now...
im the wrong person to ask
We'll wait until another helper comes by or you can post this in #study-discussion or #discussion or #serious-discussion
why the wrong person to ask buddy
also how much do you ask for chess lessons
I wanna reach 1800 elo by the end of 2026
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If you're done close the channel 
I am not done with this channel...
What else do you need? Write it down then
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1+1=?
Please dont troll in the help channels
these channels are for genuine questions
if you dont have any real questions, you can close this with .close and move to #chill for joking around next time
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is there some clever matrix multiplication method to find sum of elements of a
oh damn
x^t A x for x=(1,1,1) but I dont think thats gonna help here
well adj A is symmetric if that helps
adj(adj(A))=|A|^n-2 (A)
use det(adj(A)) = {det(A)}^n-1 for det(A)
then plug det(A) into this to get A
choose the negative solutions, as det(A)<0
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i want that shoutout in june 😡
yeah
"he was such a strong support throughout this journey especially with his funny jokes that kept me going"
💔
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Regarding 1 how can I integrate it? I have tried parts and I tried making a sub. Nothing works.
Well I feel you dont have to integrate it for this one 
Maybe some kind of reciprocal trick
Furthermore, it doesn't even have an antiderivative
Well I looked at that option too. I had $\int_1^x \frac{log t}{t+1}dt+\int_1^\frac{1}{x}\frac{log t}{t+1}dt$ I wasn't sure how to proceed
BigBen
Really? no tricks of any sort for it?
Ok
u = 1/t might give something dont you think ?
Why is there a - in front of the 2nd integral if I may ask?
yeah i'm pretty sure it works
Sorry that should be a plus
Let me see
But we have neither u or du in our integrand?
Do you know u substitution?
think bout log properties
But I then have $\int_1^\frac{1}{x} \frac{log\frac{1}{u}}{1+t} (-t^2du)$
BigBen
replace every t
change the bounds
I did. For f(x)
oh alright
i would rather do it with f(1/x)
but it works
i suppose
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can someone help me integrate this
is that a 1 next to cos
yes
$\int \cos(x) dx = \sin(x) + C$ so you just need to do substitution
pi_day
do you know what u equals in terms of t?
right. then solve for what dt equals in terms of du
is that a separate question
no
or how is it related to this
the question is to integrate that
where does this come from
its the fraction numerator
right. why do you need to integrate it?
write out exactly what u equals in your u sub
ok
i see. your du/dt is incorrect
$\frac{d}{dt} \lp \frac{n \pi t}{5} \rp = \frac{n \pi }{5} \frac{d}{dt} t = ?$
pi_day
oh yh because t would be 1
the derivative of t with respect to t is 1 yes
is this a seprate problem?
yes
looks fine. get a number and post it here or check with wolfram
,w int 0 to pi sin(x) dx
use that as a template
@rain sentinel Has your question been resolved?
cos(n * pi) depends on the value of n. write out a few numbers and try to find a pattern. also you can't divide by 0 when n=0 so solve that case seprately.
Well, what happens if you substitute 0?
for t yes. i was talking about the step after that
if you sub zero the term becomes 0
@rain sentinel Has your question been resolved?
I already answered that here
@rain sentinel Has your question been resolved?
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For 5b if we are generating a solid of revolution don't we need to know what the shape of the cross sectional area. Because can't the shape because a square or a circular disk, etc
"rotating it" would imply a disk
any other shape would imply it stretches during that rotation
@left trail Has your question been resolved?
Ok thank you for making it clear.
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ABCD is a rectangle such that AB=68 and AD=27, E,F,G,H is shown like the diagram. AF=BE=CH=DG=54. find the shaded region
ok so i wanna know why this is inccorect (ik its convoluted but i just wanna know why)
... ok nvm i see why lmao
brah
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hey can anyone help with this question from div curl and all that
i got till c part , can someone give me a hint for how to do d part
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gauss law is just $\phi = \frac{q_{en}}{\epsilon}$
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How do I check one-one property?
Uh, is it one to one nvm misread it
Well, usually you assume that T(f) = T(g) and then try to prove that f = g
x+3=21
!redir
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actually i am not getting how do we start or deal such questions
!occupied
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Start with the definition
Do you know what a linear map is and what a kernel is? If yes, you can probably use bloubbloub's way, if not, look at the definition of one to one
Assume T(f) is the zero function (that's what T(f) =0 means)
Can you do something to T(f) to get back f(t) ?
a kernel when all the maps goes to zero vector
i am not sure what does it mean?
can we take any simple example?
What is the derivative or how do you compute definite integral
by applying integration and then we put limits in the last integral
and derivative and integration are quite opposite things
y=x^2-->y'=2x
integration of y'= x^2+c
So how do you differentiate the integral function
Or how would you compute the definite integral then two ways to solve it
leibeneiz rule?
we put values of limits in functions
Yeah I mean like can't you see the answer at that point?
Indeed but there is something more fundamental
i can't because it is my first time of solving such things
why do we apply derivative but
i know you want to say that both the function would be same so we will get =0
it is constant function
so it is not one-one
am I right?
$\forall x, \int_0^x f(t) dt =0$
bloubbloub
So what must f be
0
What is the map that maps to the zero vector
Explain further
kernel
Kernel is a set
it should be kernel
What function is that
zero function
You got it then
i am not getting it
why do you guys not say things properly
you can see how i am stuck
What are you not getting
or maybe i need to understand all the things on my own via youtube only
What is one-to-one?
f(x)=f(y) implies x=y
^ Yes in this case you would do this
Then arrange it in this form
Then there are two ways to go about it
Essentially the end goal is to show that the function f and g are the same
You should write it down, there are two ways either by the definition of one-to-one or by showing the kernel only contains the zero map, I am not sure which way are you doing
Second way
Do you understand why to show that T is injective it suffices to show Tf = 0 ⇒ f = 0 (Tf identically zero implies is f identically zero)
I will try
I will take two functions f and g
T(f)=T(g)==>f=g
T(f-g)=T(f)-T(g)
Sooo T(f-g)=0
Yeah Tf=0 then f=0
I can see you understand why but you need to present your workings in a much more organised way
I will I will it's my first time
Thanks
How do I check onto?
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It is not true that T is onto
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Need help with number 6
If u don't mind can ik which grade u are in?
I am in uni
Am I still supposed to be in highschool to post here?
no limitations of that sort.
Cool
@autumn osprey Has your question been resolved?
The fact that limits are brought up at all suggests to me that the limit definition of the derivative will be used
Yeah i was thinking of that like using the fact 1 is a particular limit of ln
f has a nutty definition and the derivative existing is weird to me
Bro!!!
From another mother?
Yes?
Sry for asking same question again and pinging you back @onyx peak
If we take f(x) as constant function
Will it be one-one
This channel is taken, grab a free one
Opps sry sry
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could someone with desmos experience help me graph this
never used the website
very close i think
i forgot to include the domain
The second one
!nosols please
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.
I understand that it's a bit harder in this case because the helpee is not familiar with Desmos, but chances are the point of their exercise is to get familiar with it.
right, my bad
-5 is the x if im not mistaken and y is 1
thank u so much
its the other way around
how tho
the first coordinate in the bracket is the x one
ahh
