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And then transform one of them by shifting the argument by π
Unless you have already tried something else
there is a nice trick you can use, and it is pretty easy to derive with the compound angle formula
oh ok
You mean prostapheresis?
yeah
Mmh do they help here? I would need to try
yeah it really helps
Oh Yeah you're right
Then you just make one of the factors = 0 and you're done
Nice tip👍
however its only useful is OP knows the compound angle formula
how to tranform exactly?
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should be h just because it is the orthogonal projection of f onto the space of trignometric polynomials of order 2, right?
Using cos(π - a) = -cos(a)
@timid silo Has your question been resolved?
am I looking for a quadratic when I expand out
open your own help channel please
@timid silo Has your question been resolved?
Your guess is right, but I don't think the reasoning is.
Closer usually implies some type of distance. I don't think orthogonal projection is a distance
Do you know Parseval's theorem
@timid silo Has your question been resolved?
Personally I think your original answer is ok as long as you specify why orthogonal projection leads to smallest distance
Plug in f-g and f-h for f
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I need help to find the restriction on phi
I can do everything else except that
how do I do that?
I do not know the answer to your question but what concepts are required ro solve this?
*to
BRUH
you can either
- Graph everything onto the xyz space
or - Graph out a slice of the solid, more preferably, graph out the slice on xz or yz-plane
after graphing it out, you'll see a clear bound for what phi needs to be
Mb sorry
yeah but
I need to show it algebraically
i know its pi/4
but
can I do it like this
hmm
in that case, I suppose then just change everything to spherical coordinates and solve for the intersection
I got this:
cos phi = sin phi
from this
what r
the rho that is
oh why
so you know that it is pi/4 right
basically you are supposed to find the intersection between rho^2(cos(2phi))=0 and rho^2=1, this gives you the intersection between the cone and the sphere of radius 1
now, you can indeed cancel out the rho in rho^2(cos(2phi))=0
then, you would do the same thing for the sphere of radius, and you'll see that the bounds for phi is the same for both intersections
when you cancel out the rho in rho^2(cos(2phi))=0, what happened is you just simplified this down to show you a surface represented by rho!=0, theta is any angle and phi is any angle that satisfies cos(2phi)=0. It doesn't really give you much information about the intersection.
rho^2(cos^2(phi))=rho^2(sin^2(phi))
just pull everything to one side and you'll get cos^2(phi)-sin^2(phi) which is just cos(2phi)
oh ok
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please ping me
?
Like where are you stuck
!status
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
ah
Thanks 😭
I guess 1
Hmm okay
I understand the problem
So prerequisite knowledge
but dont know how to approach it
Yeah
Can you find a relation between a and b?
a+b=180 I believe yes
Yep
Now
Do you know that property where
An exterior angle of a triangle is equal to the sum of opposite two angles
oh I did not know that, thats a geometry concept no? The year I had geometry covid scuffed it up
thats why im tryna build up my geometry and algebra foundation
please and thank you!
You can also prove it using Angle sum property of triangle , to find the angle besides Angle 1 on teh line, then use Angl 1 + that angle = 180
Will give you the same result
Can you just remind me what its called when to angle makes 180° on a line, I frogot the name
No worries
uh
supplementary
idk
i think thats it
Aye aye
kk!
It's been like 3 years since I last studied it so I have forgotten the exact names
I'm sorry
So this one, can you similarly apply to our question?
c + the other angle = a
<2?
I mean
or you talking about D
Yes
oh so
Cuz making a forumal with C wouldn't work well
D = B+C?
So you see Angle D and try something with it
since b is a vertical angle
haha lol
And also
Now something between b , c and the new angle you found?
Angle sum property
Like ykr All angles of triangle adds up to 180°
Yeah
Do it
With b , c and b+c , you just found
See they are all interior angles of a triangle??
yes
So what do they add up to?
one second lol
kk
yes
yes
The angle b can be brought INSIDE the triangle?
Like to the right side of a
Correct?
yes
hold up
Yeah
wait give me exactly 1 min
Lemme check
kk
How did you come to that?
so
in the problem
it says a= 2c
and using the angle thingy
from the top + angle c we counclude thats a
It's no property it's just given
so thats C
ya
but thats how I got c on the top
and in the problem it also said b=c-15
so instead of putting b in the triangle i put c-15
so I would get
c-15+c+c=180 for the inside
of the triangel
in the bottom
Good
That's the correct method man 😭
Like there are multiple ways
And I would have never seen that coming
Nvm
Now
You get C as?
65
ya
Good work
😂😂
Sure
say less let me take some quick pic
Okay so in these questions , key word - MUST be true
ya
alr lol
idk 💀
Anyway
probs not
So let's start
Don't make the angle signs dw
U *
Yeah
and half of it adds up to 180
q+u=s+v
yes
kk
Yeah?
but if s+v= q+u does that mean s+v=t+r?
Yeah
is that any use to us
That's correct
Yep for the third one
But to develop a thinking you must
Like Trynna think FOR the quesntion and not randomly
Like see what's given and try to find something related to it
So now what would you write ?
oh
Like substitute s with v, as we already know s=v
See
- Trynna make things in less variables
2.Trynna substitute some variable with values given in question, like straight line is there make it 180 - Sometimes just keep things as they are for future use,
ya
yes i would be able to find it
Yeah
if you give me v
Now you have to find v
Now
This one is not so easy to think, you'll get it with practice
But yeah
In teh question can you see q+u+v
What is it equal to ?
180
wiat
Sure
could you just explain from the top you did that last time and I got it super easily lol
it lowkey helps a lot
From the top?
Yeah
Except the angle you wrote equal
That's correct
Also we are given q + u = s + v
Now you knew, s = v
ya
Can I write v anywhere s appears
ya
yep
ya
Rn were solving for question 1
Which wants us to get something in terms of q and u
So now , how do you get q and u from this ?
Just wait a sec I'll be back
kk
No
nah you good
I told you it would be hard to think of as a beginner
Uhh
Yeah
q + u = 2v
Sure?
wait could you explain that
on why q + u = 2v
Okay
q + u = s + v
s = v
Therefore
q + u = v + v
q + u = 2v
Understood?
ya
Hmm good
Now find for me
Some relation between q and u
Like find some straight line or something
line C?
Umhmm
wait
Yeah
hold up my brain is thinking rn
Ikr
oh my goodness
so
would r and u be equal to 90?
idk if my brain is thinking right
Hwo did you get to that?
so i imagined there not being a middle line
just for convenience
so just lines D and A
Umhm
Yeah
ya im just totally lost on this question
We still good on that!
180
Good
So can I not just add v , on both sides of q + u = 2v
To get
q + u + v = 2v + v
180 = 3v
v = 60
wait why
Any questions?
oh
From where?
Yeah
i would have never thought of that
ya
See I asked you to find a relation between q and u
If you had done that on Line B
You would have thought of that
You see?
if u want lol
I'll write it's 1 am you say
You can ?
Nah
dam
thats unfortunate
lol
its fine
ya but i think i can solve the problem
from there
since i can find eveyr value
Accept friend req
cant
Aye
ya
ya
q + u + v = 180°
ya
We just had q + u
And in the other side v
Now if you had written , q + u = 180 - v
That would have been correct too
And also we knew q + u = 2v
Yeah but now you know?
Still this isn't what the question 1 asked right
ya
So subbing that
Yep
ya
Yeah you can
No worries
is it 60 for all of them
i see
They can be, but can't say for sure
is there a way to actually solve for all the values of the angles
with only knowing
Nah
v is 60
Nah
You can't get the values , only relations
😂😂, cya
cya
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kk
Gn
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I know they used the chain rule here but how did they get e^x(ln a) from e^(ln a)x
multiplication is commutative
${(a^b)}^c=a^{bc}$
GarlicBredFries
could you texxit that
The derivative of e^x is e^x
GarlicBredFries
By chain rule
Shouldn’t this be the final answer then
whats wrong in the last one
It doesn’t make sense why does the power of ln a disappear and why does it be rearranged to a^x where did e^x•ln(a) go
$(e^{ln(a)})^x=a^x$
GarlicBredFries
$x^{log_x(y)}=y$
GarlicBredFries
$ln=log_e$
GarlicBredFries
Ok I sorta get it
$\ln$ and $\log_e$, y'all.
Ann
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If I have 1/(3x^2 + 1) I should make u = (√3)x but what do I do if I have 1/(x^2 + 3)
Cause I can take out 1/3 and put it in front of the integral, but then I need to multiply by 3 because of du, right? Which goes in front of the integral too, but that cancels out the 1/3? This doesnt seem right....
Factor out a 1/3 first
Oke so 1/3 ∫ 1/((x^2)/3 + 1)
This one
∫ 1/(x^2 + 3)
Yes then this is the right next step
Do u sub now
1/3 ∫ 1/((x^2)/3 + 1)
u = x/3, du = 1/3, dx = 3
1/3 ∫ 1/(u^2 + 1)(3)
(1/3)(3) ∫ 1/(u^2 + 1)
∫ 1/(u^2 + 1)
arctan(u)
arctan(x/3)
Is this correct?
x^2 / 3 does not become u^2 if u = x/3
u = x/√3?
Yes
Ah oke
1/3 ∫ 1/((x^2)/3 + 1)
u = x/3, du = 1/3, dx = 3
1/3 ∫ 1/(u^2 + 1)(√3)
(1/3)(√3) ∫ 1/(u^2 + 1)
∫ 1/(u^2 + 1)
√3arctan(u)
√3arctan(x/√3)
Correct now?
,w diff sqrt(3) arctan(x/sqrt(3))
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I know that when lissajous figures are in the form Asin(B(t+C))+D that I can take 2pi/B to get the period, but the periods are different, the period of x(t) is 2pi, the period of y(t) = 4pi. What do I do to get the period of them together?
How often it repeats
More rigorously
(not me googling rigorously)
I dont really know haha its just how long the function goes before it repeats itself
a function with domain D is said to be T-periodic iff for all x in D, x+T is in D and f(x+T) = f(x)
Then, "the" period of f is the smallest T such that f is T-periodic
(ignore the case where this min doesn't exist)
1 moment I need to read this a few times to make sure I understand haha
Here you have a function from R to R^2, f(t) = (x(t), y(t))
By R^2 do you mean like the 2nd value of k?
What's k ?
An integer
oh
sin^-1({0}) = pi Z
Never seen Cartesian products ?
Ah I thought k was to do with the period haha
Maybe but I dont recognise the name I will google them
Cause then the notation of powers makes a lot of sense
No I dont think so
But otherwise no, R^2 is just the set of all pairs of real numbers, i.e. 2D space
I think I get what you mean by this tho
Like I just take the lowest common multiple of 2pi/B, right?
Cause you don't say sin is 42pi periodic, even though it is
This trick saves so much time
You want a period of x and y at the same time
Yeye
I wouldn't call that a trick
I didnt understand how to get both together but now its kinda obvious haha
oh
Well whatever it is its handy 😅
Thanks again!!
❤️
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If $x+\frac{1}{x} = 4$ what is $x^6+\frac{1}{x^6}$?
babario
use $a^3 + b^3 = (a+b)(a^2-ab+b^2)$
Dissrupt
@timid silo
oh right okay
okay i think
so
Uh, okay, we have this equation, like x plus one over x equals four. And we need to find x to the power of six plus one over x to the power of six. To get that, we use this expression with x squared plus one over x squared, which is, umm, (x plus one over x) squared minus two, I think. So, that's like 16 minus two, which is, umm, 14, I guess.
Now, we can use 14 in the main expression, which is x squared plus one over x squared whole cubed minus three times x squared plus one over x squared. Let me plug in 14 and see what we get. So, it's 14 cubed minus three times 14. Doing the math, it's, umm, 2,744 minus 42, maybe?
So, the final answer is, 2,744 minus 42, which might be, 2,702. Yeah, I think that's it, but not entirely sure.
took me time that
and dont lecture me that i cant explain well
i already know
you can do stuff like this here actually $x + \frac{1}{x}$
babario
just make sure u wrap the latex round $$
hmmm okay
yeah alr, i was unsure throughout as i dont usually write out my whole thought process
as i think i may actually be getting some parts wrong
your answer is correct
@frank monolith i got it correct?
uhh so ur main expression is ${(x^2 + \frac{1}{x^2})}^3 - 3x^2 - \frac{1}{x^2} = x^6 + \frac{1}{x^6}$?
babario
oh wait, whose question is this?
mine
confused screaming
this is correct right?
hmmm im not sure
im pretty sure its
$x^6 + \frac{1}{x^6} = \left(x^2 + \frac{1}{x^2}\right)^2 - 2$
Avaaaa
no
nah
dam
you are missing a 3 with -1/x^2
u said cube previously
tats squared
but your expression wont be much useful
oh
hmmm right
so this then
$x^6 + \frac{1}{x^6} = \left(x^2 + \frac{1}{x^2}\right)^2 - 2$
Avaaaa
nope
wait no
i did the wrong thing again
dam i got it before
now its just
well i got it right the first time so, oh well
so in the end its $x^6 + \frac{1}{x^6} = (x^2 + \frac{1}{x^2})(x^4 + \frac{1}{x^4} - 1)$?
babario
Dissrupt
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i expanded the LHS and also worked from RHS but got stuck
can you show your work
@fossil spoke Has your question been resolved?
FLASHBANG
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Square the sum and simplify, then noting that the original sum is positive you can take square root again
There is no need for trigonometry
you mustve done something wrong
1/sqrt(2)-1 is not equal to sqrt((1/sqrt(2)-1)^2)
@digital jay
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HELP can someone show me working out
Do you know basic trigonometry?
Can you show your work? 🙂
🙂
no worries! 🙂
find the length of the adjacent first forgive my possible spelling error
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“graph the function y=4(cosX)^2 from -2(pi)<_X<_2(pi)
Usually we use <= and >=
Can you graph just y = cos(x) from -2pi to 2pi?
tell me if this looks right let me try
so 4 is a stretch factor
does that effect magnitude?
so can (cosx)^2 be negative?
no
so does it like bounce off 0 or something?
either 4 or 1
yeah, like it only goes that high
isn’t that the default
but there is a 4
so it goes higher than default
perhaps, up to 4?
so would the equilibrium be 2?
so 4cos^(x) has max of 4*1 = 4
ohhh okay
that makes sense cause it is just stretching it vertically
i’m trying to think, if the middle line isn’t 0, is it just the average of 4 and 1?
so 5/2
why?
.
I think so yes
let me think
no because that would mean a side length would be 0
and that’s not possible
but I feel like i’ve seen 0 in a calc after putting in cos(x)
,w plot cosx
is cosx zero somewhere?
yes
so will cos^2(x) be zero?
why is that?
you havent studied cosx?
isn’t taking like cos(90) like not allowed?
because the opposite is the hypotenuse?
why is that
.
i dont think i understand that?
like
say you have a triangle right
if you put yourself in the 90* corner
the hypotenuse is always the greatest side of the triangle, and there id no greater angle than 90, therefore, the opposite side of the 90* angle would always be the hypotenuse
do you know the quadrants?
yes
@steady lodge Has your question been resolved?
@steady lodge Has your question been resolved?
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in this video professor leonard posts about this "figure 8" shape and says that greens theorem is not applicable to this case because it is not a "simple curve". Why must the curve be simple?
I know that green's theorem only works on "simple curves", but why?
the curve still encloses a region (2 regions)
it's because the curve is going around one region clockwise and one region counterclockwise
it's for morally the same reason that this integral is 0, even though it looks like the area enclosed is > 0
@inner spear Has your question been resolved?
I'm a bit uncertain - do you mean that they will have opposite signs of magnitude?
Hayley
you're effectively reversing your bounds
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is it possible to numerically/algebraically show that 1. as x increases y increases; 2. as x increases y increases at an increasing rate for the following equation. The domain is restricted to Pi/2
The domain is restricted to (0;Pi/2)
sure, take the derivative
i tried and got the following expression -3/8 (sinθ/θ)^((-11)/8) ( cos(θ)θ-sin(θ))/θ^2
yeah now show that's > 0
this looks better
for your domain
and you get as far as i got it x<tan x
and then i am stuck
and taking a second derivative of this hell doesn't look plausible
so perhaps there is a different way or am i missing something?
well
it might be possible to prove something about sinx/x
and apply that to your function