#help-33
1 messages · Page 196 of 1
get the quadratic
its fine
make it in vertex form
what would that look like
ya
ohh
divide by 2 on both sides
yes
then plug in
factor out -5/2
average of roots
is ur width
and plug into the L formula
to get length
okok
I factored out that and i have A= -5/2(w^2 + 24w) now what do i do
uh so now complete the square
(B/2)^2?
im not gna be able to solve it like that on the test cuz my teacher wont give me the mark
and subtract -5/2b^2 outside
she wants me to get the 3rd term inside the brackets
ok
what third term?
like how its aX^2 + bx + c
c
She wants us to get C
Wat
let me copy paste wat my friend said
you have x^2 + bx + c = 0. solve for x. rewrite it as x^2 + bx = -c. now complete the square, you're gonna add (b/2)^2 to both sides. x^2 + bx + (b/2)^2 = -c + (b/2)^2. the left side is now a complete square, so it's the same as (x + (b/2))^2 = -c + (b/2)^2
ye
imagine u did that all on one side
of the equation
and imagine ur c=0
ill give u a different way
so
the way i copy pasted
.
ya
kk
so can u ask someone else to help u mate
kinda getting late for me now
just when u find the complete square
the inside part should equal 0
so like it should be w-12 is 0
so w is 12
and L is whatever u solve
i gtg now though so good luck on ur exam
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Uh why's my calculator not answering did I input it wrong?
You need parentheses
You wrote it down under with the fraction
Your calculator doesn't know the numerator is the whole thing, it just sees -6^2
Uh ill see if I got it
and u also need another ) at the end bc ur inputting cos(number, and u didnt close it
mhmm
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Hello I have a question, how do we do arithmetic operations on nonexisting limits? for example liml(x+sinx) as x goes to infinity? because lim sin(x) doesnt exist, but lim(x) does and it is infinity
you generally hope to compare the limit to something easier to deal with
eg here x+sinx>=x-1 and x-1 diverges, so x+sinx also has to
yeah i get it from an intuition point of view but if i write that in a homework or exam ill get a very well rounded 0 lmao
what i meant is how do we do it formally
that is a legit rigorous argumentation
its the comparison test
otherwise you can just check the epsilon def of divergence
oh you meant bigger or equal
my apologies im blind
yes
thanks man
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ok so i have a silly problem, i can solve this kind of questions with three numbers just for some reason i can't figure out how to do it with 2. sorry for the shaky writing. (is this how you ask for help here?
this is Cramer's rule right?
it isn't difficult i just got to figure out how to multiplay it then i can find x,y,z,w
pretty sure yeah
yeah then you just forgot how to calculate 2 by 2 determinants right
the determinant will be just ad - bc
right so for this spesificly
wouldn't that be right?
ok yeah it is the right answer thank you a lot :)
no worries!
I'll just close this channel then
.close
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you want to be able to use the distance formula
that requires knowing Ax, Ay, Bx, By right?
what the hell is that
but then to find those you just apply right-angled trig
the same thing as Pythagoras
yeah but we dont have that in physics
The distance thingy
the question just wants the C vector
YOU DO!!!!
i dont see it in the solution tho
otherwise use the cosine rule, that's another option I guess
they've done this calculation
but they didn't mention the distance formula explicitly
I'm telling you that's what they used
Okay yeah... But why is Ax the mag multiplied by sin
you can calculate it yourself from the solution
right-angled trig
your 60 degrees is labelled wrong
that angle should be 90 - 60 = 30 degrees
okay this might sound stupid asf... But what is right angled trig and when do i use it
so $A_x = -26 \cos 30, A_y = 26 \sin 30$
south, just south
This math video tutorial provides a basic introduction into trigonometry. It covers trigonometric ratios such as sine, cosine, and tangent. It explains how to evaluate it using right triangle trigonometry and SOHCAHTOA. In addition, it explains how to solve the missing sides of triangles and how to find the missing angles using inverse trig f...
awh hell nah 😭
are you self-studying?
this is my first year of uni but in highschool they didnt teach us well
yeah then unfortunately you're playing catch-up
Do i just have to watch that video
cause these are like STEM fundamentals, trigonometry, algebra-precalculus, and I guess stats as well
this is probably like physics I or something at your uni I guess
and you need to do a ton of practice
to succeed
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Ik its in french but i just need to prove this inequality 😦 could anyone help
c'est xi * xj en bas ?
oui

essaie de développer et de voir ce que cela peut faire
732-76=
732-70-6=
662-6=656
stop spamming
they here
Literally called the purge lol
Im so bad at math
ong
ducoup tu as essayé de developper ?
oui, rien
arctan(quotient) < pi/6
And it becomes
0 < arctan(xj) - arctan(xi) < pi/6
u mean pi/3?
No
arctan(sqrt(3)/3) = pi/6
That would be for arctan( (3)^(1/2))
arctan squar three is pi/3
.-.
yes but thats whats in the problem no?
It's given 1/ (3)^1/2
@hazy verge see it now?
i think we will use rolle for this
or mean value theorem
ngl me too but i found this in the chapter
<@&286206848099549185>
sorry I don't speak french, is the goal to find just a pair x_i, x_j with that inequality holding? or that for any i, j
Obviously xj > xi
to prove that it exists yes
im so lost ngl
sorry trying to come up with something
what math course is this? just to know what concepts are relevant
Could just use induction
We could just set different range of values for x1 and x7 to prove its existence
Like x7 could be infinity
And x1 be sqrt(3)
This a sequence that would be true for this inequality
im in hs and this is the mean value chapter tho idk how i can use it here🥲
for calc
hmm this actually does look like some MVT could work here, let me ponder
hmm j doesn't even need to be bigger than i I don't think, since if x_i *x_j is sufficiently negative the sign flips right?
xi*xj could be inferior to one tho
right but we can't assume there isn't a pair with i > j such that the lower bound of 0 works
hmm true
either way ill ask my prof tmrw if anybody is still interested leave a dm
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im a 14 yr old home sick really struggling with this question on a test thats due today. not asking for exact answers, just a simple explanation on how to solve it
question is 'write an equation for each graphed line' which im unsure how to do
what are they asking for? equation of the line?
so linear funtion could be writtern in mx+c
where m is the slope
do you get a hint now?
yes man. thank you
absolute lifesaver
all i needed was a refresh on those specific letters
.close
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I tried proving that 2^k . j choose 2^k+1 will be odd but failed, and i tried using binomial theorem but failed, and induction but failed
Its obviously true for powers of 2
But if they are not idk how to prove that atleast one will be odd
@potent temple Has your question been resolved?
<@&286206848099549185>
(a C b)
= a!/b!(a-b)!
try (nCr) where r is the largest power of 2 smaller than n
for n not a power of 2
this should work
This no?
But i did not manage to prove it
do you know Vp ?
Greatest power of p that divides smth?
yes
I mean i dont know its properties but the lte lemma
actually there is a method without vp n
yk that nCr = n-1Cr-1 + n-1Cr
try using this
oh
Oh yeah i do
good
if you still dont get it, this image might give you an idea.
Okie
No i dont get it
@potent temple Has your question been resolved?
For n=2^k you can easily prove by induction: If P(x)=(1+x)^n=1+x^n+2T(x) (where T(x) is some polynomial with integer coeffs) then P(x)^2=(1+x^n+ 2T(x))^2=1+x^(2n)+2S(x) where S(x) also has int. coeffs.
And if n=2^k * d, where d>1 is odd, then you have (1+x^(2^k)+2T(x))^d=1+d*x^(2^k)+2S(x), so we see that coefficient at x^(2^k) is always odd.
@potent temple Has your question been resolved?
I will read it thx
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Let $f(x) = \frac{-xlnx}{1+x^2}$ if $x \ne 0$ and $f(0) = 0 \ \$ 1) prove that f is continuous in $]0, +\infty[ \$ 2)a) prove that $\forall x \in ]0, +\infty[ , f(\frac{1}{x}) = -f(x) \$ 2)b) prove that $\exists \alpha \in ]0,1[ , f'(\alpha) = f(\frac{1}{\alpha}) \ \$ 3)a prove that $\forall x \in ]0, +\infty[, -xln(x) \le \frac{1}{e} \$ 3)b) deduct that $\forall x \in ]0, +\infty[, f(x) \le \frac{1}{e} \$ 4) We admit that $\alpha$ and $\frac{1}{\alpha}$ are the only solutions to the equation $f'(x) = 0 \$ a) prove that $f(\alpha) > 0$ and $f(\frac{1}{\alpha}) < 0 \ \$ b) Prove that $f'$ is continuous in $]0,+\infty[\$ c) Prove that $f'$ doesn't change its sign in every one of the following intervals: $[0, \alpha]$, $]\alpha, \frac{1}{\alpha}]$ and $[\frac{1}{\alpha}, +\infty[$
i am not able to do anything past 3)b)
Froggy
how do we prove that $f(\alpha) > 0$ just from the fact that $f'(\alpha) = 0$
Froggy
$\text{and the same for } f(\frac{1}{\alpha}) < 0$
Froggy
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did you figure it out?
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if PACF gives us the direct correlation between an observation Yt , and Yt+k , why do we care about ACF ?
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Can someone check if I did problem 50 correct
@shy shard Has your question been resolved?
@shy shard Has your question been resolved?
No, the region revolves about the y axis so you should use the washer method with dy integral
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0
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What is pi x x.?
you gotta be a bit more specific
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oh ok ty
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How do I find the inverse laplace of this?
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You have the opportunity to purchase a pair of x-ray goggles that will allow you to see through exactly 1 door before the battery runs out. How much are you willing to pay for these goggles?
How is this different from monty hall
here you can directly just say that the probability becomes 1/4
!original
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@vital juniper Has your question been resolved?
original problem:
You're on a gameshow and are tasked to choose the lucky door. Behind 1 door is $10,000. The remaining four have nothing. How much are you expected to win?
part 2:
You have the opportunity to purchase a pair of x-ray goggles that will allow you to see through exactly 1 door before the battery runs out. How much are you willing to pay for these goggles?
!show
Show your work, and if possible, explain where you are stuck.
also, considering it has absolutely nothing to do with the Monty Hall problem, i'd say it's quite different
On monty hall you have two choices, and on the second you already have knowledge.
On this one you only make one single choice
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why cant i find the area under the curve by integrating with respect to x axis? and the video wanted to integrate with respect to y axis?
what do u mean by this?
cant i just sqrt both side?
Y = SQRT x
you can also integrate the function of difference of the the values of y for a given x
so basically intergral of 2 * sqrt(x)
so x is a function of y but y is not a function of x?
y=+-sqrt(x) 1 input value yields 2 outputs not a function
Yes
ok than i have a qn if i just have a x=y^2 graph
can i integrate it to find area?
from maybe 3 to 0
wrt to x axis
can i integrate like this to find area? @limpid pond @sweet pawn @trail hamlet ?
seperate qn
If you want you would need to integrals
one for the sqrt(x) and the other for -sqrt(x) and it’ll yield zero
ok so i add them together?
wait why though. if you integrate the difference, aren't you ultimately calculating the are
the original problem had a line. that would make the region non symmetric
This will yield the area inside the curve rather then area under the curve tho
then can we subtract the y coord of line with the sqrt of x? isnt that the same thing as taking two integrals
yeah but to find area under the curve just divide answer by 2?
Oh nvm
The line ends before the origin
im so confused rn
this is a new seperate qn
jus this graph alone
The area under the curve of this function of y (integrating with respect to y) doesn’t equal the area inside the function (integrating with respect to x)
is it possible to find area inside the function with respect to x?
from x = 0 to x = 3
If you bound it to the x axis then yea
but the question you showed above states the area between 2 functions
Referring to this
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stop snitching dawg
no
why are you angry ?
because idk how to solve the cubic discriminant
like derive it
from the form ax^3 + bx^2 + cx + d = 0
Cubic discriminant damn
maybe you can find something useful searching the cardano formula
the regular one is easy i even derived it myself but this one hard
NO
i have to derive it myself
no cheating
first try with depressed cubic before doing with the original cubic equations
that helps
alr fine
ax^3 + bx + d = 0
this right?
yeah
okayyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
x^3 + x(b/a) + d/a = 0
ok i will play around with this equation
thanks gng
yw
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In triangle ABC angles A = C45°. Side a is 20 m. Calculate height hb and sides b and c.
,rccw
What have you tried?
Nothing
Cause I don’t know what to begin with
I can’t do Pitagoras
Bc I only know C
hit: sum of angles in triangle is 180
What's the angle of B then
90°
this might help
Use the Pythagorean theorem now
Now when you have all angles you can calculate sides. You have square triangle.. so it’s pretty easy
That’s like using cannon on fly
b is the hypotenuse
Ok I get it
hi swerriee ily 
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can someone give me some suggestion on where to start
what have you tried?
What's eqn (*)
@vocal cloud Has your question been resolved?
the fourier transform equation
nothing yet. i was hoping someone could give me some kind of hint so that i can start. i dont need the answer, just some kind of guide
first thing you can do is expand the first integral using the definition of F(k)
how do i expand it? use by parts?
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Hello guys, how are you doing? I need help with this complex numbers problem; it's honestly really simple and I can't believe I am yet to figure it out:
I need to find a polynomial p(x) ∈ R of minimum degree such that the solutions of the equation z^3=-8i are roots of p(x) and p(i)=-3
Here's where I got to, I now believe I should multiply that P(x) with their respective conjugates... but I have no clue how to multiply them all
If the solutions to $z^3=8i$ are roots of $p$, then you can start with the polynomial $q(z)=z^3-8i$. Then just let $p(z)=\alpha q(z)$ and solve for $\alpha$ to satisfy $p(i)=-3$
SWR
So how would I solve q(z)=0 with complex numbers? Don't I need the trigonometrical ecuation for complex numbers?
Why do you need to solve q(z)=0?
I may or may not have thought of something
I may not have a brain, but I've had an idea
Hm?
Give me a min I'm trying stuff in my sheet here
Thanks for the help, I'll be back in 5
Well, I'm back... I didn't get much further
alpha HAS to be a real number according to the image right?
Why did you do +8i?
Oh i missed that the polynomial needs real coefficients
Okay that adds some wrinkles
mb
No wait, it is -8i
Oh your problem showed $z^3=-8i$ i see
SWR
Yeah... Already asked 5 AIs about it and they all answer something different
ok so
he wants p(i) = 3 and p(z) = 0
well for starters you can solve the equation by converting -8i into is exponential form
once you get that, establish a polynomial P(X) = Q(X).(X-z1).(X-z2).(X-z3)
he wants P(i) = -3
Q(X) would be degree zero in this case and you would solve for it
Brother this was the first topic we saw as review
I'm preparing the obligatory final
At the bottom of the pic there's P(x)
I would need to do their conjugate
HOLD ON
I do see a pattern here
buddy he said minimal degree
you don't have to do conjugates
just the 3 roots would do
plus the constant that verifies P(i) = -3
But they're complex
If we're talking about a polynomial p(x) ∈ R
Look
@wide osprey Has your question been resolved?
If you need the real coefficients, then do $P(z)=\alpha (z^3-8i)(z^3+8i)$
SWR
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how would i approach this? (This is discrete math)
we have to manipulate this expression in a way that allows to take the limit to give us e.
i think we can represent everything but the 2 as a sum rule of some binomial coefficient, just not sure how.
i cant progress other than that i can represent that as c(n,k) times 1/n^k
i believe you can approach this algebraicly or using the sum rule
rewrite the binomial coeffs using the factorial formula
so itd be
lim as n ap -> inf of 2 + n!/(k!(n-k)!) * 1/n^k
,w n!/(k! (n-k)! n^k)
yeah
we care about the input here correct? not the others
i mean we could put it ontop but i dont see how that helps
i write it out and like,if we get k at 0 = 1 , wouldnt that go above the num of the expoenential? since u have 2 and then k at 0 is 1, it becomes over??
@uncut forum Has your question been resolved?
<@&286206848099549185>
Ok i figured out the first 2 terms give a 1, when k = 0 and 1
so i see why the +2 exists now,
not sure what to do after
ok <@&286206848099549185> i got an extra thing,
now we can represent that as n times n-1 times n-2 ... times n-k +1, since we can divide it by n-k, which leaves us with k! on the denominator with n^k, not sure what to do with it though.
I got an idea of how to do it
If you expand every combination( i.e) nC1=n!/(n-1).1!
nC2=n!/(n-2).2!
yup
I will take what i did photo
Try to use the binomal formula
Expanding the choose term is not the way I think you're supposed to do it
like the sum rule of x^k-j*y^j ?
Yeah
$\parens{a+b}^n = \sum_{k=0}^n \binom{n}{k}a^kb^{n-k}$
RedstonePlayz09
Notice how the right side is similar to what you have
Well not really
They are just hidden
What did you choose for a and b for this to fit into your case?
If you make a good guess you'll see that it fits for the first terms aswell
But focus on the general term first
like you mean i try to represent this from the start with the bionomial coefficient?
wait
the other term is a 1?
Try to take your sum, and express it as (a + b)^n for some a, b
There are specific a, b that you can choose, for which if you take (a + b)^n, and expand, you get exactly the sum in your limit.
so (1/(n^k) +1) ^n?
Close
What is k?
k is only a variable that appears in your summation. it's the index variable.
What do you mean bounded?
No
Your original expression contains only n
(1/n^k + 1)^n has k in it
And if you put that in the summation, although it now has only n, it's just wrong
Maybe it'll be easier if you first take your sum
2 + (n choose 2) * 1/n^2 + ...
And write it in summation notation
THEN use the binomial formula
i dont get what you mean, it has k in it but it doesnt ?
you mean i write the same exact thing in the question in summation form?
Yes
Refer to this if you are confused
Turn the sum there into summation form
so the sum up to n starting at k = 0 of n choose k times 1/n^k ?
when its n
RedstonePlayz09
when k = n it stops
Now it's just a special case of this
So what a, b give you the sum you want?
wait for if it goes for every single number, that means, the second element b is k ?
No
Just try to see what you can plug in to a, b so that you get this sum
uh idk if i understood what you said wrong, but i tried to plug in if n was 2 and i tried to do the sum at 0 1 and 2, i got 1 for both 0 and 1 but i got 1/4 for 2
because 2! cancels with 2! and 0! is 1
We already said the sum you have is this
Are you trying to check it?
For k = 0 you get:
$\binom{n}{0} \frac{1}{n^0} = 1 \cdot \frac{1}{1} = 1$
RedstonePlayz09
For k = 1 you get:
i thought by observing some pattern we'd get b
$\binom{n}{1} \frac{1}{n^1} = n \cdot \frac{1}{n} = 1$
RedstonePlayz09
yes
That's the first term in your sum
For the rest, it's exactly as written
For example, the (n choose 2) * 1/n^2 is just k = 2
So this sum is correct
All you have to do it use the binomial formula now
$2 + \binom{n}{2} \frac{1}{n^2} + \binom{n}{3} \frac{1}{n^3} + ... + \frac{1}{n^n} = \sum_{k=0}^n \binom{n}{k} \frac{1}{n^k} = ?$
RedstonePlayz09
Left side, what you have
Then we got this sum
Now using the binomial formula, this should be equal to...?
the exponential?
?
oh wait
Use the binomial formula
express it in (a+b)^n ? To be able to do n choose k times that?
You just write it as (a + b)^n
Because that's not a summation anymore
It's a very simple expression which you'll be able to take the limit of
Find a, b for which:
$\sum_{k=0}^n \binom{n}{k} \frac{1}{n^k} = \sum_{k=0}^n \binom{n}{k} a^kb^{n-k}$
RedstonePlayz09
i have no idea other than a being 1/n^k and b being a 1
am i missing something
wait
Plug in a = 1/n^k to the right side
You wont get back the left side
b is 1 yes
a is not 1/n^k
umm, does it have to do with a being 1/n^k which can be expressed as n^-k and that ^k gives 1?
so its one?
No
Ok first I told you that b = 1 is correct
Plug that in
And look what you have left
The a^k term needs to become 1/n^k
What is a for this to happen?
does a have to be negative then?
so if they have same exponent they have the same original num at the non ^ of k so they are the same so a = 1/n?
or you just take the root for both sides of k
You just notice that when a = 1/n, you get the 1/n^k term
Now take the sum with a^k * b^(n-k)
And plug in a = 1/n, b = 1
And make sure you understand how you get the original sum
I have to go now, but the final step is to plug in into (a + b)^n
That will be equal your sum
And then just evaluate the limit
Good luck
ok i will try , thank you man
Np
ily tooo <3
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use the laws of exponents
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i was wondering if I could get some help on where to start. I've been stuck on this problem for a couple of days
this is what I've thought of so far
first the cup itself is always parallel to the tangent line at a point it's on, so that means that it is parallel to g'(x), and so would that imply that the slope itself of the water spilling = g'(x)
the larger |g'(x)| the larger the magnitude of the rate of change of the volume of the cup gets and so there is a positive correlation between the two. So then the crux of this question is to find the relation btwn g'(x) and the ROC of volume of the water.
the volume of water = h(w^2) and that can be written as 2w^3. But it's at this point i get stuck. I was thinking maybe since the width of the cup is parallel to g'(x) we can sub it into that but I don't know if that makes sense
i'm trying to think of it as a related rates problem and idk if that is the right approach and there are other concepts connected to it
@valid plinth Has your question been resolved?
Hello. I think might have overthought a bit. See if you catch this: the amount of water remained is determined by the biggest absolute value of slope (equates g'(x)).
ohh okokoay so thats what i was thinking right now
the largest the slope can be is 2
in terms of absolute value
Right
but from there i thought that maybe
we find the angle the made between the graph with a slope 2 and the horizontal axis
and the angle of elevation could help
but i don't even know if that is right
i don't think that is what you're insinuating either with this
It's a square cup remember?
the base is perpendicular to the side, so the minimum slope of the side is 1/2
So the diagonal of the cup is parallel to the x-axis
in that case
that's how you contain the rest of the water
I'm sorry I don't think I'm following, the side of the cup is 2x that of the base because the side is = 2w and the base is w^2
could I see a sketch of this then if it is possible
sorry for the rough sketh
It has nothing to do with the volumn of water
the base is w and the height is 2w
right
You agree this is the position that spills most of the water right?
yea i agree
At after one spill no more can be spilled out unless there's a larger |g'(x)|
yea I agree with that part too
Now draw a diagonal of the cup starting from the top of the triangle
See that line? That's parallel to the x-axis.
Below that is the water you can contain
exactly half
ohh okay i see
and so this is exactly half of the square and thus half of the volume of the cup
Yes
that makes sense
how can i come to this conclusion mathematically without drawing a picture
because now it seems obvious if i draw a picture
First, the surface of the water is always parallel to the x-axis
this is commonsense so you don't really need to explain here
yes i see
So the largest angle the cup is turned determines the water remained
at that point it would be when the slope of the tangent is the largest which is 2
Yes
Which happens to be the "tangent" of your cup
h/w = 2
I got to go, see if you can phraze it better
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how would I go about solving this?
I started with this:
KXLI
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Let $E/F$ be a Galois extension with Galois group $G$. Let $f \in F[x]$ be a polynomial and let $a, b$ be roots of $f$ in $E$. Is there always a $\sigma \in G$ with $\sigma(a) = b$?
DavidL1450
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<@&286206848099549185>
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I need to find the z coordinate of the center of mass of a wire described by $\vb{r}(t) = (t\cos t, t\sin t, 2\sqrt{2}t^{3/2}/3)$ where $t \in [0, 1]$.
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what the answer
what have you tried?
wrong
!noans
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
third one idk
the angles are labelled
can you label the vertices
you will see why its important in a minute
@raw sand
ping me when you get back
<@&268886789983436800>

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area of parallelogram formed by body diagonals is twice the area of the original parallelogram
area of parallepiped formed by face diagonals is twice the area of the original parallelopied
does this follow in higher dimensions? just curious i have no idea
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I was trying to implement the letter "A" from the font OCR-A. I ran into the problem of not knowing how to find the distance from the zero line to the bottom line of the "A". I think I came up with a solution that works, but I am not entirely sure.
Basically, I wanted to find the length of a line that both intersects each sides of the isosceles and is parallel to the base line. I think the following method could work:
- Start measuring from the point that both of the equal sides meet, then measure to the base in a perpendicular manner.
- Take the height from the base to the desired "new base" and subtract that from the total height.
- Take the current remaining height and times the original base length to get the "new base" length.
In the photo, the new base is colored in red. The drawing is a bit of a mess, so if you want me to further clarify, just let me know.
The OCR-A letter.
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hello I need help proving that the number of non-increasing functions from N to N is equal to continuum
firstly can I just say that it is <= continuum as there are continuum functions from N to N?
wym by there are continuum functions from N to N?
the number of functions from naturals to naturals is equal to continuum
yeah, the cardinallity of a subset is always <= than the cardinallity of the set itself, you just need to consider if you need or not to include the proof for the cardinallity of the functions N to N
ok great
this was proved in the lecture
so to prove >= I have to construct a function which is onto from the set of these functions to a set with cardinality continuum correct?
what about this: every function is uniquely defined by the infinite sequence f(1),f(2),..., define a function g(x) = 1 if f(x+1) < f(x) else 0
oh but infinite 1's isnt a value ever
ugh
What set do you consider cardinality of continuum?
I tried set of all binary sequences
All functions?
wait wym
I think that could work
Yes it should
I think i got this
how
f(0)=0
f(n)=f(n-1)+1 if nth term in a string is 0
f(n)=f(n-1)+2 if nth term in a string is 1
by string you mean binary string?
sorry im a little confused we need an onto function from binary strings to our functions or from functions to binary strings
cuz I thought we need the latter
y
<= here
oh so this
works
why is this function an injection tho
If you have 2 different sequences
Take the smallest different term
Then f(n-1)=g(n-1)
Thus
f(n)=f(n-1)+1
And g(n)=g(n-1)+2
So f(n) and g(n) are different
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Am I right so far?
Your graph of g(x) is wrong
Trying to plot the graphing by plotting the points is a good approach
Try it again,it isn't (0,-4)
Rather than converting it into a quadratic and using the formula for finding it's roots making a big mess and a huge chance of going wrong
I didn't quite understand it
Which one?
It's the same as 2.c
But reverse and they haven't mentioned a relation ,but it's already given in the table
:p it's not the same
Nice
@wheat pewter Has your question been resolved?
Is it 8?
Yep
Raeee
Uhm
I need help with the rest😭
The one I did the mess with and the uhm other incompleted ones
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i got using snells formula that a) is 30 degrees
but how do i do b
@worn field Has your question been resolved?
@worn field Has your question been resolved?
@worn field Has your question been resolved?
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@worn field Has your question been resolved?
could you maybe show me a diagram of the
angle of indiedcen at the second interface
i dont quite get that part
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how to find C?
@cosmic raptor Has your question been resolved?
You can consider x'(t)
look for which gamma you get x'(t) > 0 or < 0 for all t
I tried doing it
positive whjen 1/2 * sech^2(6*t) which was there, i tried putting it as an interval but still wrong
show
[ x(t) = 4t-\gamma\tanh(6t) ]
[ x'(t) = 4-6\gamma\sech^2(6t) ]
𝔸dωn𝓲²s
So consider first x'(t) > 0
,, 4 \geq 6\gamma\sech^2(6t) \Leftrightarrow \gamma \leq \frac{2}{3\sech^2(6t)}
ahh i mislooked the question then
i just tried solving it again, apprently incorrect
wait, wouldn't it be 2 / 3*sech^2(6t) ?
oh yea
apparently, still incorrect 😦
ya hold on
The max value of sech²(6t) is 1
so the least value for gamma would be 2/3
gamma < 2/3
ohh yeah that's true
Now the other case
i just typed it in and it partially worked
so now i'm curious, why is it <=
and not just <
𝔸dωn𝓲²s
i considered strict monotony
\textbf{2. Case} : $x' \leq 0$
[ \gamma \geq \frac{2}{3\sech^2(6t)} ]
𝔸dωn𝓲²s
but like why is it <= thought?
let's say it is equal two 0 and function is neither increasing nor decreasing
wouldn't there be 2 values of x with the same y?
wait, that's for multivar calc, we're not there yet hahaha
no
so with x^3
so function is increasing when x>0
when x=0, it's not moving at all so 0 and so on would be strictly increasing
makes sense
but when do we know when to use < vs <= ?
here <= is sufficient
we just gotta make sure the derivative doesn't cross the x-axis
so either above or below x-axis
sorry, i'm confused
