#help-19

1 messages · Page 104 of 1

clever fjordBOT
glad wadi
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okay

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I think I got it now

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thanks

olive sparrow
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you can also put the 4 as 2^2

glad wadi
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ahh

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okay

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I got it now

olive sparrow
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$((2x+1)^2+1)$

clever fjordBOT
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clonesolopros

glad wadi
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how does it get to that

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i understand the

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4 * 1/4 turning into 1

olive sparrow
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$2^2(x+\frac{1}{2})^2 = (2(x+\frac{1}{2}))^2$

clever fjordBOT
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clonesolopros

glad wadi
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goated

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thanks

olive sparrow
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fr

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well idk if it helps with the integral

glad wadi
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it does doesnt it?

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because I can put it into the arctan

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and that will be my term

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for u

olive sparrow
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well you can do u = 2x+1?

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and its about the same thing

glad wadi
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did I do anything illegal

dawn tiger
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everything is right up until you evaluated the integral at the last step

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from this formula, your u is (2x+1) and your a is 1

glad wadi
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oh so its just flipped?

dawn tiger
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the problem is the 1/(2x+1) out front

glad wadi
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how do I know which is the u and which is a?

dawn tiger
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when you plug those into the formula, you should get 1/(1) * arctan((2x+1) / (1)) + C

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the u is the thing that you're integrating with respect to

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if you let u = 2x + 1

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then du = 2dx, so this integral becomes 1/2 * 1/(u^2 + 1) du

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then you know that the antiderivative of 1/(u^2 + 1) = arctan(u)

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so your answer would be 1/2 arctan(2x + 1) + C

glad wadi
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ahh

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okay

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where does the 1/2 come from though?

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nevermind

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I got it

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lets go

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.close

odd edgeBOT
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odd edgeBOT
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west pecan
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I just want to verify that I'm understanding this correctly

west pecan
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is this a proper proof that the set is closed under addition?

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I feel like I don't understand my own justification even if it's right lol

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to verify that it's closed under addition, that'd be the same as verifying that f+g (where g is a member of the set) is also a member of the set for all g right?

odd edgeBOT
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@west pecan Has your question been resolved?

west pecan
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is this the right thought process? did I do it right?

granite slate
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In my humble opinion, you need to show that for every f, g satisfying f'(-1) = 3f'(2) and g'(-1) = 3g(2) and for all real number r, you have f + g and r*f in your set.
(Furthermore, I feel like you show nothing actually, you are simply writing what you want to show without explaining why this is true :/)

west pecan
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okay wait let me try again

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that makes sense

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is this correct?

granite slate
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Yes, this is a lot better !

west pecan
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I still feel don't feel confident that there isn't a counterexample for g

granite slate
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Such as ? f and g play the same role here

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(Actually, you also have to check that your set is not empty, by proving that the constant null function is in your set)

west pecan
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well it's assumed that it's on the interval (-4,4) so it can't be empty I think

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oh yeah I'm just concerned about closure under addition rn

granite slate
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What do I want to say with this stupid example is that you still need to check that your set is not such an example too

west pecan
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oh wait you're saying I have to show that the set of differentiable real-valued functions on the interval (-4,4) such that that property holds isn't empty?

granite slate
west pecan
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oh

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well f(x)=0 satisfies that property as one of the conditions for a subspace anyway

granite slate
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Absolutely

west pecan
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and then for scalar multiplication I wrote

granite slate
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But in order to have a complete proof, you need to mention it

west pecan
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yeah my question here was just about verifying the closure under addition

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I feel confident with the other conditions

granite slate
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Okey, sorry

west pecan
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tyyy though

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ur good

granite slate
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No problem

west pecan
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.close

odd edgeBOT
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odd edgeBOT
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limber willow
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for n(c_n), should the lower bound not be 0? if not im not really sure how to do this

odd edgeBOT
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@limber willow Has your question been resolved?

limber willow
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Actually I just kept as is and and voided using c_0 does this work

olive sparrow
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isnt $\frac{d}{dx}(x^n) = nx^{n-1}$

clever fjordBOT
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clonesolopros

limber willow
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hence nx^n instead

olive sparrow
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but why

limber willow
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to express (nc_n) in terms of f(x)

olive sparrow
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btw do you know what is f(x)?

limber willow
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yea the basic egf of c_n

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its in the question

olive sparrow
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well its the function e^x

limber willow
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only if c_n = 1

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i dont really see where this is going

olive sparrow
limber willow
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wdym

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i think it wants me to use c_n and c_0 to express (nc_n)

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just cant find a use for c_0

olive sparrow
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like this?:$c_n = \frac{x^n}{n!}$

clever fjordBOT
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clonesolopros

limber willow
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yea

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we need $\frac{n * c_n * x^n}{n!}$

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wait no

clever fjordBOT
limber willow
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given

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$\frac{c_n * x^n}{n!}$

clever fjordBOT
olive sparrow
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but doesnt it tell you to find the sequence: $c_n$?

clever fjordBOT
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clonesolopros

limber willow
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no just the egf for nc_n

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for n >= 1

olive sparrow
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well its the same thing

limber willow
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how

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multiplying by n shifts the factorials in the dominator down by 1

olive sparrow
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and is there a problem?

limber willow
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yea its not the same

olive sparrow
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its like saying: $\frac{n}{n^2}$ is not equal to $\frac{1}{n}$

clever fjordBOT
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clonesolopros

limber willow
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not the same at all lmao

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thanks for tryin pal

olive sparrow
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step1: calculate c_0

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$c_0 = \frac{x^0}{0!}$

clever fjordBOT
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clonesolopros

olive sparrow
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$f(n) = \frac{x^n}{n!} =c_n$

clever fjordBOT
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clonesolopros

olive sparrow
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$n \cdot f(n) = \frac{x^n}{(n-1)!} = n\cdot c_n$

clever fjordBOT
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clonesolopros

odd edgeBOT
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odd edgeBOT
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mystic saffron
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Im learning about cylindrical coordinates and I’m wondering if there id a reason that there is a z axis but no x or y axis or why whoever made the coordinate system chose to include z instead of x or y

mystic saffron
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Oh wait I’m dumb

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It’s because the x and y axis are a part of the polar coordinate system?

green elm
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yes, the x and y get converted to polar representation, and z is left alone

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the choice of leaving z alone is kind of arbitrary

mystic saffron
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Ok

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.close

green elm
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you can equally well do cylindrical coordinates with y and z converted to polar, or x and z convered to polar

odd edgeBOT
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mystic saffron
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Thanks

odd edgeBOT
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odd edgeBOT
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chrome zodiac
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Hi

odd edgeBOT
chrome zodiac
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Where do I start?

dawn tiger
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it might be useful to notice the change of base formula

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log_x(y) is the same as ln(y) / ln(x)

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you can use that to rewrite log_p(a) as ln(a) / ln(p) and log_p(b) as ln(b) / ln(p)

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now try using that same change of base formula for log_ab(p) and see if you get something that looks similar to your known information, perhaps by using some other log properties

odd edgeBOT
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@chrome zodiac Has your question been resolved?

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mystic saffron
odd edgeBOT
mystic saffron
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i acquired the aos but im still stuck on the rest

shut wedge
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The axis of symmetry passes through the vertex yes?

mystic saffron
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yeah so i'd have my first coordinate but i don't know where i'd go from there

shut wedge
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If you have your x coordinate, how would you find your y coordinate

shy bramble
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can you help me with geometry?

mystic saffron
shut wedge
odd edgeBOT
shy bramble
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oh sorry

shut wedge
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Its made up of x and y isnt it?

mystic saffron
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yeah

shut wedge
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So cant you use that to find your y coordinate?

mystic saffron
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wait do i just plug it in

shut wedge
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Yep

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:\

mystic saffron
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oh my god its right in front of me

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im sorry man im tired as hell

shut wedge
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Lmao allg

mystic saffron
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i cant even think critically

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okay let me just

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figure that out

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assignment aint takin it for some reason, i dont know where i messed up

shut wedge
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Bruh

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You need rest

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-9(-1)^2 aint 9^2

mystic saffron
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because of the parentheses right

shut wedge
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Yea

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Its not in the parenthesis with the square

mystic saffron
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i got 8

shut wedge
mystic saffron
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yeah assignment took it

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oh BROTHER one last thing man

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thatll be it

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let me check if my tescher had a video for it (he didnt for this one)

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okay yeah he didnt

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this is like the last foreign concept and thatll be over

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yeah never mind im good

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off to bed now! thanks man

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.close

odd edgeBOT
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dry plank
#

Hello I asked for help with this question over the weekend however I’m sort of confused.

dry plank
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This is what I was told.

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Since I can’t use sine can I instead use cos?

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Or is that also wrong?

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Wait I figured it out, we have to use the cos function

chrome zodiac
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Whether u use sine cosine or tangent is dependent on what values u were given and what u r trying to find

dry plank
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Tan is out of the picture.

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But cos helps me determine what the value of ST is.

odd edgeBOT
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main musk
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Translation: Solve the following inequalities I am confused about question C, how do I factorize it properly like A and B

frigid canopy
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yes?

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have you tried graphing it?

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it doesn't have any real roots

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notice that

noble forge
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math*

main musk
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It difficult to me despite me enjoying doing random calculation in games ;')

frigid canopy
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try completing the square

noble forge
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or maybe the quadratic formula

main musk
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I did it where I do ac and the sum of b

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but it gave me -3 and 2

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well specifically -6 and -1

frigid canopy
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right?

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ooh

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my bad

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yeah

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quadratic formula should work here

main musk
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when is the quadratic formula applied btw?

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when it ax^2 + bx + c?

noble forge
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the quadratic you mentioned has no restrictions and the quadratic formula has no restrictions

main musk
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oh so aslong as there is a,b and c I could use the quadratic formula to find x?

noble forge
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(talking about complex number system)

main musk
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seems like something very important to rmber forever lol

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so far I have -x + √-2x -24 / 12, if I were to do -24 - 2x it would be -26 but √26 is like 5.1, idk if normal or I am messing up somewhere

ember oak
clever fjordBOT
main musk
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oh alright thank you

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.close

odd edgeBOT
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odd edgeBOT
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ocean hamlet
#

can somebody please explain? i got them all wrong lol

odd edgeBOT
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Please don't occupy multiple help channels.

ocean hamlet
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Consider the relation R on the set of natural numbers greater than 10 defined by xRy if x^2 > y. Which properties does it satisfy?

frigid canopy
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mind translating the options?

ocean hamlet
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symmetric, transitive, irreflexive, antisymmetric, reflexive

waxen frigate
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Any germans in here it is about stochastik and analytische Geometrie

ocean hamlet
odd edgeBOT
ocean hamlet
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it's not reflexive because x^2 is not greater than x^2

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it's not symmetric because if x^2 > y then y is not greater than x^2

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hence it is antisymmetric and antireflexive

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and it is transitive because if x^2 > y and y > z then x^2 > z

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whats wrong?

odd edgeBOT
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@ocean hamlet Has your question been resolved?

odd edgeBOT
#

@ocean hamlet Has your question been resolved?

odd edgeBOT
#

@ocean hamlet Has your question been resolved?

fickle coral
#

But x²>x for given conditions on x and that relation is xRx

marble bridge
ocean hamlet
marble bridge
ocean hamlet
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@marble bridge

marble bridge
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now that i think it may be irreflexive:

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the relation is irreflexive because it doesnt not have the property of reflexivity

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@ocean hamlet

ocean hamlet
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its marked wrong

marble bridge
marble bridge
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so no element can be related to itself under this relation,and that makes it irreflexive

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@ocean hamlet

ocean hamlet
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. close

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.close

odd edgeBOT
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odd edgeBOT
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tropic gulch
odd edgeBOT
merry finch
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What have u tried

tropic gulch
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i dont know what goes inside the integral

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i have the bounds though

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outer integral is from 0 to 2π

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inner integral from 0 to √theta

merry finch
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If you want the area

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Then you just want the integrand to be 1

tropic gulch
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oh shit i forgot

merry finch
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Remember that a 2d integral is doing the volume under the surface

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And the cross section * 1 (height) would be the volume

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Which is also the cross section aka the area

tropic gulch
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so its not this

merry finch
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Well idk I can’t do a double integral ins my head

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Can you show your working?

tropic gulch
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wait i misclicked

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yeah sure

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here

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apparently its wrong

gaunt steppe
tropic gulch
#

@merry finch

merry finch
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Huh

tropic gulch
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<@&286206848099549185>

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pleas

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@merry finch

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@dawn tiger could you help me with this

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got it nvvmmm

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.close

odd edgeBOT
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odd edgeBOT
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mystic saffron
#

HALP

odd edgeBOT
mystic saffron
#

ok this question wants to trick me

dawn tiger
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what do you know about the angles in a triangle?

mystic saffron
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they add up to 180

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the thing is

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x+59 and x+51 dont have te degree

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so should I ignore the angle

dawn tiger
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?

mystic saffron
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since it's only asking for the measurement

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it doesn't have a degree simble

dawn tiger
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that isn't really important it's assumed that they're degrees

mystic saffron
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and even then it would give me a - number

dawn tiger
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since the 84 is in degrees

clever fjordBOT
#

Pro_Hecker

dawn tiger
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but yeah

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why not just solve the equation?

mystic saffron
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ye ik that

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it gives me a negative tho

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is that possible?

dawn tiger
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(x+59) + (x+51) + 84 = 180

undone basin
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yes

dawn tiger
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you get a negative for x

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the actual angle is positive

mystic saffron
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oh ok

dawn tiger
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x isn't your angle

mystic saffron
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then ye that was my question

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also already solved

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but how do u know which letter is which

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i'm still having that thought

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like is d the right angle

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and be is both y-5 and 13?

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because if u used y-5=13

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y=18

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then u plug it in

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18-5=13

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so since it shows on both sides

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and it is congruent

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fr?

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thenwhat r the measurements for

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so AD is 5x-5?

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dc is x+12 or 5x-5?

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ah

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5x-5=x+12

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so would u solve 5x-5=90?

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since its a right triangle

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and u r trying to solve for x

odd edgeBOT
#

@mystic saffron Has your question been resolved?

olive sparrow
odd edgeBOT
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mystic saffron
odd edgeBOT
olive sparrow
#

$5x-5=90 \implies x=19$

mystic saffron
#

yes

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wait

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huh

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95/5

olive sparrow
#

then we have $(x+12) \implies (19+12) = 31$

clever fjordBOT
#

clonesolopros

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clonesolopros

olive sparrow
#

31º is the angle its asking

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@mystic saffron

odd edgeBOT
#

@mystic saffron Has your question been resolved?

odd edgeBOT
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grand hound
#

just having personal wonders, does this formula work if I choose a number z=a+bi and then I want to take it to the (c+di) complex power like
z^(c+di)

grand hound
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it makes a lot of sense to me

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but I may be wrong in some point

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you basically start at z = r * e^iθ

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z = r * e^iθ

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r = sqrt(a^2+b^2)

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so that's a real number and therefore you can turn it into e^ln(r)*e^2kπi

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with any integeer k I guess

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so that's how you get
(e^ln(r) * e^2kπi)^(c+di) * (e^iθ)^(c+di)

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so then you do lots of distributive

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pretty trivial

spice geyser
#

$e^{2k\pi i}$ is just 1

clever fjordBOT
#

qwertytrewq

grand hound
#

yes I know

spice geyser
#

ah but for c+di

grand hound
#

ya

#

so I can turn |z| into e^ln(|z|)

spice geyser
#

usually ud just put it with theta

grand hound
#

yes but theta is the one for the first complex

#

theta is the argument for z

#

and I turn |z| into polar coords to work with it as a power of e

spice geyser
grand hound
spice geyser
#

better put it should be (e^ln(r) )^(c+di) * (e^iθ* e^2kπi)^(c+di)

#

where e^i(theta+2kpi ) is determined by branch

grand hound
#

so I just take e^2πki as 1

#

and then times e^ln(r) just the same thing

#

oh makes sense

spice geyser
#

as long as you specify your theta from specifying a branch

#

it should be good.

#

the branch is where you pick you 2kpi factor

#

everything else is defined around it

grand hound
#

theta is for z tho

#

right?

spice geyser
#

z^c= e^{cln(z)}

#

which is identical to your definition

grand hound
#

yes

#

what's a branch tho

#

me no english

spice geyser
#

say if my number is i and our brach is (0,2pi]

grand hound
#

the branch is theta?

#

oh

#

ok I get it

#

no no I get in now

spice geyser
grand hound
#

is like

#

ok

#

yes

#

go on

spice geyser
grand hound
#

ya

spice geyser
#

if my branch were (pi, 3pi]

#

$\log(i)$ would be $\frac{5\pi}{2}$

clever fjordBOT
#

qwertytrewq

grand hound
#

also that

#

yes

spice geyser
#

so, you could imagine that your e^{2kpi} is chosen already by choosing the branch

grand hound
#

ok but the theta for r would always be 0

#

cuz it's a real number

#

so I just take e^ln(r)(c+di)

#

which is r^c*e^ln(r)di

spice geyser
#

but, the angle 2kpi is added to the imaginary part of ln(specific number)

grand hound
#

but r is the modulus of z

spice geyser
#

since you separated into reals and imaginary, you dont need to do it twice for real and imaginary

#

however, if you view r not as the modulus of z, rather as a complex number, there might be a 2kpi multiple

spice geyser
grand hound
#

I'm confused

#

if I think about r as a complex number

#

what now?

spice geyser
#

sorta like that

grand hound
#

yes

spice geyser
#

for z, the modulus is r (nothing needs to be done for the modulus, no angle needs to be added), and the argument is theta

grand hound
#

yes

#

for z

spice geyser
#

👍 so is this clearer?

grand hound
#

what's the conclusion then?

spice geyser
grand hound
#

wdym by might have an argument

spice geyser
#

by argument i mean arg(z)

#

the angle

grand hound
#

like the theta

#

but of r

#

ok but like

#

it's ok if I take r^(c+di) = r^c *e^ln(r)di

spice geyser
#

it should be e^ln(r)(c+di)

grand hound
#

isn't it the same?

spice geyser
#

for example (-1)^(1/2) could be i or -i

grand hound
#

it does cuz I just had to add this

spice geyser
#

(1)^(1/4) could be i, -i, 1, -1

#

but in your formula 1^(1/4+0i)=1^(1/4)* e^0=1

grand hound
#

wasn't the square root of a number always positive by convention?

spice geyser
grand hound
#

oh ok

#

then

spice geyser
#

is -1+i more positive than 1-i?

#

so, thats why we do branch cut

#

which, if you do different kinds of branch cut, you will have all the possible solutions

#

it would be a weird generalization if we single out real number and force them to satisfy some positivity clause

grand hound
#

ok I get it

spice geyser
grand hound
spice geyser
#

but not the other outcomes

grand hound
#

wdym one outcome

spice geyser
#

you would get 1 on the right side no matter what branch you pick

grand hound
#

oh cuz

#

e^ln(1) is 1

#

or

#

cuz d = 0

#

one of those I'm guessing

#

not sure which one

spice geyser
#

so no matter what ln(r)di=0

#

so you get e^0=1

grand hound
#

but you also have r^c

spice geyser
#

r^c is just 1^(1/4)

#

i thought u r using the real definition here

grand hound
#

and isn't that like the 4 possible numbers

grand hound
#

T.T

spice geyser
grand hound
#

I should be studying algebra and not this

grand hound
#

that's why I want the formula for

spice geyser
grand hound
#

oh no

#

I mean like

spice geyser
#

r^c as powers in complex would yield different result

grand hound
#

that's half of the formula I'm using

mystic saffron
grand hound
mystic saffron
grand hound
#

just joking

mystic saffron
#

hehehehe

spice geyser
#

i was pretty sure it is real power

mystic saffron
#

z^5

spice geyser
grand hound
#

yes but

#

still could give complex

#

if you consider

#

em

spice geyser
#

you are using e^ln|z|c =|z|^c

grand hound
#

what you said

grand hound
spice geyser
#

e^(real number) is real

spice geyser
#

because the left hand side is always real

#

but the right hand side could be complex

grand hound
#

wait

spice geyser
#

Ah also forgot to mention that, e^z is defined without branch cut

grand hound
#

but that's not the formula, you have to multiply by e^ln|z|di

spice geyser
grand hound
#

yes

spice geyser
grand hound
#

I have to change that to e^ln(|z|c)?

spice geyser
#

because |z|^c as power of real number does equal to e^ln(|z|)c

grand hound
#

but like you see how I got to |z|^c right?

spice geyser
#

it works if you assume that you are doing exponentiation in reals

#

which is fine

#

you can't say that |z|^c is a complex power tho

grand hound
#

I'm trying to get exponentiation in complexs

spice geyser
spice geyser
#

BTW

#

$$z^{a+b}\neq z^az^b$$

clever fjordBOT
#

qwertytrewq

spice geyser
#

for complex numbers

grand hound
#

for z complex

#

?

#

amazing

spice geyser
grand hound
#

wdym for a, b complex T.T

spice geyser
#

so, if your derivation is of complex powers, it would be wrong

grand hound
#

I think it is

#

completely wrong

spice geyser
grand hound
#

but like

#

if they're both complex you can add them

#

and get just another complex

#

ok makes sense tho

#

cuz

#

yeah yeah

#

i'm dumb

#

so like

#

it was all just my schizo

#

sad moment

#

I'll go back to studying

spice geyser
grand hound
#

.close

odd edgeBOT
#
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odd edgeBOT
#
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late terrace
#

Could someone help explain their approach to this question? I don't need an actual final solution since it's so tedious, I'm just curious as to how someone else might apporach to solve it

late terrace
#

My orignal method was factor out 100, bring it out the integral, and integrate (10+t)e^(whatever), but left me with quite a long integration by parts process

dawn tiger
#

this seems like something they'd seriously expect you to do with a calculator

#

especially since they talk about rounding to the nearest dollar

olive sparrow
#

integrate e^(1-t/20), and t·e^(1-t/20)

late terrace
#

man i hate this question

#

I just did it my original way, a seperate way where I split the (10+t) into the e^(whatever), so that I have an integral of 10e+te, and I can just evalaute them seperately

#

and both are different answers from the online calculator

olive sparrow
#

$1000e\int_{0}^{20} \frac{1}{e^{t/20}}dt + 100e\int_{0}^{20} \frac{t}{e^{t/20}}dt$

clever fjordBOT
#

clonesolopros

olive sparrow
#

$100e\int_{0}^{20} \frac{10+t}{e^{t/20}}dt$

clever fjordBOT
#

clonesolopros

odd edgeBOT
#

@late terrace Has your question been resolved?

#
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eternal glade
#

Hey guys

odd edgeBOT
eternal glade
#

Let A be a symmetrical 3x3 Matrix with eigenvalues a1 < a2 < a3. I shall show that F has a saddle point at v2 (eigenvector to a2)

#

Is there an easy way that gets around calculating every second derivative?

#

25?

#

wdym?

#

nice

lethal spoke
#

<@&268886789983436800>

mild elk
#

Knock it off

#

If you're gonna contribute to these channels, then do so

#

If not then get out

#

Idk maybe

#

This has nothing to do with the topic of this channel

#

So leave

eternal glade
#

😵‍💫

lethal spoke
#

<@&268886789983436800>

#

Spam

green elm
mild elk
#

Thanks for making this easy NotVoid

#

Oh wait he can't hear me

#

Because he's dead

#

Ripperoni pepperoni

green elm
#

bye bye whoever you were haha

raw palm
eternal glade
lethal spoke
mild elk
#

Yeah Bungo keep in mind the ||x||^2 term in the denominator

eternal glade
#

but i dont know how to prove it without the Hesse matrix

mild elk
#

That can cause some shenanigans

eternal glade
#

and i dont want to calculate the hesse matrix

#

because even one of the derivatives would take up over on line of my paper

mild elk
#

Probably try to compute directional derivatives at v_2?

eternal glade
#

thats a bon idea actually

mild elk
#

But at the other eigenvectors

eternal glade
#

yeah

#

that would do it

green elm
mild elk
#

The intuition is that if you approach it along the eigenvector of the larger eigenvalue the function is probably going up

#

And along the smaller it's probably going down

mortal trench
#

hint: maybe use the fact that this matrix is symmetrical somehow.

mild elk
#

(For reference I literally had to Google what a saddle point was so I might be royally talking out of my ass)

eternal glade
mild elk
#

(But this smells like a thing that might make sense)

pastel orbit
#

Dami helps in the help channels now?!

#

awesome! lisayay

raw palm
mild elk
#

Lol I popped in to handle a moderation matter

raw palm
mild elk
#

And was like you know what while I'm here this is more interesting than guiding middle schoolers through systems of two linear equations

mild elk
eternal glade
mild elk
#

Apparently a saddle point means not a max or a min

raw palm
mild elk
#

So I'm guessing that if you pick a direction and say f is going up

#

And if you pick another direction and say f is going down

#

That feels pretty saddle-y

pastel orbit
green elm
#

doesn't the derivative also have to be zero in order to qualify as a saddle point?
think f(x) = x^3 at x=0

pastel orbit
#

that's why

mild elk
#

🤷 again I might be making no sense at all since idk multivariable calculus

mild elk
eternal glade
#

wait im stupid, i completely failed at imagining it, obv. your right

mild elk
#

But I'm guessing proving that it's critical shouldn't be too hard

#

Overall the point is, you don't want to compute partial derivatives in xyz

#

But since A is symmetric

eternal glade
mild elk
#

Use an orthonornal eigenbasis

green elm
#

ah got it

raw palm
mild elk
#

That feels like the better way to go about life. Even if it boils down to computing the Hessian, compute it "in the eigenbasis"

#

(Probably)

#

(Maybe)

#

(Idk)

eternal glade
#

nah, your right, the directionals already do the job

mild elk
#

Oh nice

#

Talking shit really does work more than it has any right to

eternal glade
#

hahaha

valid tapir
#

Hello

#

I don't suppose anybody wants to help me with my maths revision please

#

I have an exam tomorrow

odd edgeBOT
#

@eternal glade Has your question been resolved?

#
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surreal mountain
#

im not sure where to start with this surface integral

surreal mountain
#

im used to having a given integrand, f(x,y,z) and surface(s) for the bounds

green elm
#

f is constant on the sphere, yes?

surreal mountain
#

idk?

#

i dont get what f(x,y,z)=g(x,y,z) is doing

#

seems like it does nothing

green elm
#

where do you see f(x,y,z) = g(x,y,z)

surreal mountain
#

i mean f(x,y,z) = g(sqrt(x^2+y^2+z^2))

green elm
#

well what is the value of x^2 + y^2 + z^2 on the sphere?

surreal mountain
#

4

green elm
#

ok

#

so on the sphere, you have f(x,y,z) = g(sqrt(4))

#

which is what?

surreal mountain
#

2

green elm
#

certainly not

surreal mountain
#

sqrt4 = 2?

green elm
#

yes

#

so then you have g(2)

#

which is what?

surreal mountain
#

-5

green elm
#

right

#

so what is f(x,y,z) on the sphere?

surreal mountain
#

-5

green elm
#

yes

#

which is just a constant

#

so what does the integral simplify to?

surreal mountain
#

ah

#

so all that information just to tell you the integrand is -5

green elm
#

yep

surreal mountain
#

do i still need the sqrt of partials + 1

green elm
#

kind of convoluted but in the end it's simple

green elm
surreal mountain
green elm
#

no, that's if you're parameterizing the sphere i believe

#

here it's simpler

#

you have $$\int_S (-5),dS$$

clever fjordBOT
green elm
#

you can pull out the -5 because it's constant:

#

$$-5\int_S dS$$

clever fjordBOT
green elm
#

what is $\int_S dS$?

clever fjordBOT
surreal mountain
#

S

#

but what about bounds

green elm
#

no, that's not what the notation means

#

it means "integrate the surface area of the sphere, over the entire sphere"

#

the result is just the total surface area of the sphere

surreal mountain
#

ik but how do you get the surface area if there is no bounds

green elm
#

there's a simple formula for the surface area of a sphere

surreal mountain
#

4pir^2?

green elm
#

yes

#

and what is r in your case?

surreal mountain
#

4

green elm
#

no..

surreal mountain
#

2

green elm
#

that's r^2

#

yes r = 2

surreal mountain
#

so 16pi is the answer?

#

-5 didnt contribute?

green elm
#

for $\int_S dS$ the answer is $16\pi$

clever fjordBOT
green elm
#

you still have to multiply that by -5

surreal mountain
#

i see

#

thank you

green elm
#

sure

#

cheers

odd edgeBOT
#

@surreal mountain Has your question been resolved?

#

If you are done with this channel, please mark your problem as solved by typing .close

#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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tiny inlet
odd edgeBOT
tiny inlet
#

is this right?

#

also having trouble with this one,

latent scaffold
# tiny inlet

This doesn't really look like it's in a "completely factored form", but it depends on what they're looking for.

#

For the complex one, what is i^2?

tiny inlet
#

uhh im not sure i cant remember if i^2 is -1?

#

or is considered -1

dawn tiger
#

i^2 = -1

latent scaffold
tiny inlet
#

0?

latent scaffold
#

Yes

tiny inlet
#

i^7(0)

#

i dont know what i^7 is

dawn tiger
#

doesn't matter what it is

#

what's it being multiplied by?

tiny inlet
#

unsure

dawn tiger
#

you got that 1 + i^2 = 0
so you got i^7 * 0

dawn tiger
#

so if i^7 is being multiplied by 0, can you know what that answer is without needing to know what i^7 is?

tiny inlet
#

0?

#

so the answer is 0?

#

i guess the a + bi threw me off

odd edgeBOT
#

@tiny inlet Has your question been resolved?

#
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sturdy plume
#

What does it mean by "The set is the line defined by the vector"

dawn tiger
#

every point in that solution set is of the form r * (2, -1, 1)

#

(2, -1, 1) is a particular vector in R^3, you can imagine scaling this vector by r which would lengthen it, shrink it, flip it backwards, etc. and see that every vector in that space lies on a line that contains that vector

desert marlin
#

Very poorly worded for someone who should understand linear algebra enough to teach a. Course on it

mental ridge
#

that took me like 3 readings to understand

desert marlin
#

Well and it’s even worse because infinitely many vectors work as a solution

sturdy plume
#

I'm sorry I didn't understand that, this has been kind of difficult for me

dawn tiger
desert marlin
#

The solution space is spanned by:

#

Provide a vector

#

It should say soemthing like that

dawn tiger
sturdy plume
#

Sorry no

#

That's my fault

dawn tiger
#

every solution in the set is a scaled version of that vector (2, -1, 1)

#

you're scaling by some parameter r

#

when you scale a single vector by a parameter, it generates a line

#

for example, imagine you were in R^2 and the solution set was (r, r)

#

that's the same as r * (1,1)

#

every vector in the solution set is a scalar multiple of the vector (1,1)

#

if you can imagine the space containing all solutions of the form (r,r) and considering every possible value of r

#

this forms a diagonal line, you could think of this as y = x

#

so scaling a vector produces a line

#

in linear algebra, we say that that line is "spanned" by that vector

sturdy plume
#

what im understanding so far is that the vector 2,-1,1 which were the parameters I found are like the borders for everything within the vector?

dawn tiger
#

maybe not the borders, but every single vector in your solution set is some multiple of the vector (2,-1,1)

sturdy plume
#

gotcha gotcha

dawn tiger
#

so that solution set is spanned by the vector (2, -1, 1)

sturdy plume
#

so I would just write the vector I put down in that box because the vector defines everything

dawn tiger
#

and what your teacher very poorly worded for that last part is exactly asking for a vector that spans that space

sturdy plume
#

Its an online course and im fighting out here to understand anything

#

thank you very much

#

.close

odd edgeBOT
#
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odd edgeBOT
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rose belfry
#

im having difficulty with logic, on the third row of the truth table, how is it that the overall statement is true when M is false?

rose belfry
#

would M not have to be true in order for the entire statement to be true

drowsy root
#

$P \implies Q$ is always true whenever $P$ is false

clever fjordBOT
#

Flappie

drowsy root
#

the only time when $P \implies Q$ is false, is whenever P is true but Q is false

clever fjordBOT
#

Flappie

rose belfry
#

so does the truth value of P not matter if Q is true?

drowsy root
#

indeed

#

ignore my deleted messages :)

rose belfry
#

ok, so in this specific question, M is P and N is Q?

drowsy root
#

no, they swapped it

#

thats why i was confused

rose belfry
#

is P always the antecedent?

drowsy root
#

\begin{table}
\begin{tabular}{|c|c|c|}\hline
P & Q & $P\implies Q$\\hline
T & T & T\\hline
T & F & F\\hline
F & T & T\\hline
F & F & T\\hline
\end{tabular}
\end{table}

clever fjordBOT
#

Flappie

rose belfry
#

does the biconditional q supercede the p -> q conditional in any way?

drowsy root
#

P is the antecedent and Q is the consequent

rose belfry
#

(talking about the top table which is correct)

drowsy root
rose belfry
#

$P \implies Q$ is false but the overall statement is true even though it is biconditional

clever fjordBOT
#

stwizzy

drowsy root
#

this line right?

rose belfry
#

yes i meant the compound statement on the right

#

what makes that T

#

because the consequent is F and the antecedent is T

drowsy root
#

you have M which is F, and n->m which is F, they are both false, so iff is true

serene terrace
#

A <-> B is true if (both A and B is true) or (both A and B is false)

drowsy root
#

\begin{table}
\begin{tabular}{|c|c|c|}\hline
P & Q & $P\iff Q$\\hline
T & T & T\\hline
T & F & F\\hline
F & T & F\\hline
F & F & T\\hline
\end{tabular}
\end{table}

clever fjordBOT
#

Flappie

drowsy root
#

\begin{table}
\begin{tabular}{|c|c|c|}\hline
P & Q & $P\wedge Q$\\hline
T & T & T\\hline
T & F & F\\hline
F & T & F\\hline
F & F & F\\hline
\end{tabular}
\end{table}

clever fjordBOT
#

Flappie

drowsy root
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hope this helps

rose belfry
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in this case n->m is A and (n->m)<->m is B?

serene terrace
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m is B

rose belfry
#

yes sorry

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ok i understand now, i was blurring the difference between the two statements

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.close

odd edgeBOT
#
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keen mirage
#

can anyone help me with understanding transformations or these problems

keen mirage
gilded shard
#

which equation do you want help on

keen mirage
#

can we start with 8

gilded shard
#

so the "a" value in this is 3, that represents how much the porabola is being stretched by

keen mirage
#

vertically right?

gilded shard
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yup

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if the a value is greater then 1 then it is being verticaly stretched

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if less then 1 but greater then 0 such as 0.1-0.9 then it is being compressed

keen mirage
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okay but how do i gragh that do i just put a dot at 3

gilded shard
#

no so basically this is vertex form so you are given the vertex which ius h,k

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you h value here is 2 coming from the (x-2) and the k value is 4

keen mirage
#

(-2,4) is the vertex?

gilded shard
#

when in the bracket you flip the sign so if it was (x+2) then your vertex would be -2,4

#

a "-" symbol in the bracket means its a positive number on the graph and a "+" symbol means its a negative number on the graph its a bit weird

#

so your vertex here is 2,4

keen mirage
#

oh

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so thats my highest point

gilded shard
#

"h" which is 2 is your x value

gilded shard
# keen mirage so thats my highest point

thats your origin depending on which way the porabola opens which is determined by the a value being negative or positive (negative means opens down and has a max value and positive means opens up and has a min value

keen mirage
#

it opens down rihgt?

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because its 3 which is positive

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doesnt the a value determine whether it opens up or down

gilded shard
keen mirage
#

oh

gilded shard
#

4 which is your k value will be the y in the vertex

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x=2, and y=4

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thats our vertex

keen mirage
#

okay i understand that

gilded shard
#

the 3 which is a value

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is telling us how much our porabola is being stretched by

keen mirage
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yea i dont understand what does stretch mean

gilded shard
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do you know the y values on the normal porabola

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41014

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a table for that would look like this

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x|y
-2|4
-1|1
0|0
1|1
2|4

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sorry its a bit messy

keen mirage
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its okay

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yea i remember learning that

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dont i plug in the vertex

gilded shard
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basically to transform your current equation into something like that you need to do certain things to the x/y values

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for y

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the equation is (a)y+k

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so (3)y+4

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and for x its x (+/- depending on what the h value is) h

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so in our case thats x+2

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so you plug the y value into that equation

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for the first 4 that would look like (3)4+4

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then (3)1+4

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and so on

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any questoins yet

keen mirage
#

ok.. kinda understanding it

gilded shard
#

ok so for our x values what do you think the equation would look like

keen mirage
#

our x value is 2 right?

gilded shard
#

yes

keen mirage
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wait thats where im lost

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how do i know what the equation is

gilded shard
#

so to find your x value equatoin you have to know what the h value is

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we klnow thats 2

keen mirage
#

okayy..

gilded shard
#

then because we know 2 is positive not negative it would be plsu 2

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and x is easier in that sence as you only have to know that

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then you plug in the x value on the chart into x+2

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so for the first one thats -2+2

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and so on

keen mirage
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oh so -1 +2

gilded shard
#

yup

keen mirage
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0+2 and more

gilded shard
#

correct

keen mirage
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okay and using those points i then plug it into the gragh?

gilded shard
#

Yes

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and thats the transformation of that graph

keen mirage
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but thats only one dont i need 2

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like x and y charts

gilded shard
#

?

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we only need one x and y chart for the equation

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your teacher probably puts the origional one and the new one next to eahcother for you to see

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x|y
-2|4
-1|1
0|0
1|1
2|4

this is the origional and then with what we went over you can make the new one

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do you know if your teacher wants you to write out the transformations in word form?

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such as translated 2 units right

keen mirage
#

probably

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i think he would

gilded shard
#

ok

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so for that we look at "a" "h" and "k"

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you know how to find those values in an equation

keen mirage
#

yes

gilded shard
keen mirage
#

a determines the vertical stretch

gilded shard
gilded shard
#

heres the equations

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list all the transformations you know and well see if you miss any ok

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or do you want me to go over them with you

keen mirage
#

ill try and tell u if im confused

gilded shard
#

sounds good

keen mirage
#

the relation has a vertical stretch by 1/2?

gilded shard
#

yesa

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but say by a factor of 1/2

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for full marks

keen mirage
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ohh okok

gilded shard
#

or BAFO if your teacher has said thats allowed just shorter

keen mirage
#

and its vertex is -4,7

keen mirage
gilded shard
gilded shard
keen mirage
#

um not rlly..

gilded shard
#

no worries

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you got the vertex right

keen mirage
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ik how to do the charts things