#help-36

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pallid basin
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yes

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when ur in like a higher math class they might make you simplify it further

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but for now thats right

clever lagoon
#

how am I going to make that positive and negative

pallid basin
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oh

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de

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dw

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u dont

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u just leave it

clever lagoon
#

it says it wrong

pallid basin
#

what.

clever lagoon
#

i swear

pallid basin
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did it say the right and

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ans

clever lagoon
pallid basin
#

okay hold on

clever lagoon
#

dawg this shit gonna take up my whole page 😭

pallid basin
#

try like

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0.92

clever lagoon
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ah hell nah

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For the square root?

pallid basin
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just

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trust

clever lagoon
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wait

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I got it right

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im so damn smart

pallid basin
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what was it

clever lagoon
pallid basin
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oh wait so true

clever lagoon
#

let me try to solve this next one on my own

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easyy

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its x=8 x=,8

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-8

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Now how is that and that in the same unit

pallid basin
#

its the same stuff

clever lagoon
pallid basin
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yeah

clever lagoon
#

easyyy]

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waity

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not perfect squaree

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let me clutch up

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give me a sec

pallid basin
#

what else does the problem say

clever lagoon
#

thats it

pallid basin
#

okay uh ig calculator

clever lagoon
#

brain smarts

pallid basin
#

so true

clever lagoon
#

GOD IM SO SMART

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alright thanks for the help im going to got to bed now

pallid basin
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no problem

final saddleBOT
#

@clever lagoon Has your question been resolved?

final saddleBOT
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sand kayak
#

I need help on this question im stuck pls help

final saddleBOT
#

@sand kayak Has your question been resolved?

sand kayak
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no

vagrant vector
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Just set P(x)=21% and solve x?

sand kayak
#

would it be 53.315?

vagrant vector
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lemme check

sand kayak
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ok lmk

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please

vagrant vector
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Wait sorry

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It's P(x) = 21, not 21%

sand kayak
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hmm yeah idk tbh im lost

vagrant vector
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uh it's not hard

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Lemme send working rq

sand kayak
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okay

vagrant vector
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X rounded is 36

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K bye I got a class

sand kayak
#

okay well thanks i appreciate it

final saddleBOT
#

@sand kayak Has your question been resolved?

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final saddleBOT
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buoyant yarrow
final saddleBOT
buoyant yarrow
#

How do u graph f(x)g(x)

manic lotus
# buoyant yarrow

You need to figure out the functions for f(x) and g(x)
Is g(x) here implied to be converging at -1?

buoyant yarrow
buoyant yarrow
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i think its (1/x^2 +2) -1

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i think im wrong

manic lotus
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$g(x)=2^{\left.\left(-\frac{x}{2}^2+1\right)\right.}-1$

soft zealotBOT
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(TR) Chrom

buoyant yarrow
buoyant yarrow
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if its too hard to explain, can u explain how to graph f(x)g(x)

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if u want

final saddleBOT
#

@buoyant yarrow Has your question been resolved?

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sturdy lodge
#

Hi

final saddleBOT
sturdy lodge
#

I need help

final saddleBOT
#

No need to ask ā€œCan I ask…?ā€ or ā€œDoes anyone know about…?ā€ā€”it’s faster for everyone if you just ask your question! See https://dontasktoask.com/

sturdy lodge
#

Anyone?

delicate remnant
tiny gorge
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this is hard to read, what's the length of the base?

vagrant vector
sturdy lodge
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This whole problem

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Base is 36cm at the bottom

vagrant vector
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u did a well

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A is right

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for the trapezium just use the trapezium formula

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or derive it yourself

delicate remnant
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1/2(summation of sides)Ɨheight

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Ig

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Parallel sides*

vagrant vector
sturdy lodge
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I dont know how to use Pythagoras theorem

vagrant vector
sturdy lodge
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Didn't understood that

delicate remnant
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What grade is it

vagrant vector
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basically short side²+other short side²=long side²

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c is the hypotenuse

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The longest side

ashen dust
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a² + b² = c²

sturdy lodge
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So it's the formula?

vagrant vector
sturdy lodge
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Then like why my teacher wrote AC²=AB²+BC²

vagrant vector
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AC is the side called a normally

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then AB is the side called b

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And BC is the side called c

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it's a better way of writing

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It uses ABC as the points instead of the sides

sturdy lodge
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Ohh but how come Ab is 8

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And Ac 17

vagrant vector
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wym

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BC is just the longest side

ashen dust
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your diagram dont even have ABC points

vagrant vector
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17 is BC not AC

sturdy lodge
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Hypotenuse?

vagrant vector
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17 is the hypotenuse

ashen dust
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8 is from (36-20)/2

sturdy lodge
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Where did hypotenuse come here

vagrant vector
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U see this right

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AC is the hypotenuse

sturdy lodge
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But it isn't a right triangle so what does hypotenuse have to do

vagrant vector
sturdy lodge
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Then where is that angle

vagrant vector
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Same height

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oh

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uh

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I forgot to write

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but I'll tell u it's a right angle

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šŸ‘šŸ‘

sturdy lodge
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Ohh thnx

vagrant vector
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k gl

sturdy lodge
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And I don't know

vagrant vector
sturdy lodge
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Why they subtracted

vagrant vector
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which part

vagrant vector
sturdy lodge
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36 from

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20

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And then divided 16 by 2

vagrant vector
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So you're left with both sides

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then try divide by 2 to find the side

sturdy lodge
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What do u mean

vagrant vector
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if u subtract 20 from 36

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Cuz 36 is the bottom

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you get left with both sides of the trapezium

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which is where the right triangles are

sturdy lodge
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20cm is connected vertically with two parallel lines and 36 covers the whole bottom right

vagrant vector
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The lines aren't parallel

sturdy lodge
#

No I mean lines inside

vagrant vector
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oh yes

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yes

vagrant vector
sturdy lodge
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Ohh to see how much is left in the whole trapezium

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We subtract

vagrant vector
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So u get left with 2 of the right triangles

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(their base)

sturdy lodge
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Then we 14

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16*

vagrant vector
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Ya

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Then there's 2 of them

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And u need to find 1

sturdy lodge
vagrant vector
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So u divide by 2

vagrant vector
ashen dust
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base is bottom part of the shape

vagrant vector
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Greens are base

sturdy lodge
#

Ohh

sturdy lodge
vagrant vector
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U see u have 2 of the green parts right

sturdy lodge
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Yea

vagrant vector
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so u want just 1 to do your equation for pythagoras with

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so what do u do

delicate remnant
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Because it's a symmetrical structure u can divide it

sturdy lodge
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Ohh

sturdy lodge
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So both will be equal

vagrant vector
sturdy lodge
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But then again we can divide 8 by 2

vagrant vector
sturdy lodge
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Cuz why not simplify in the simplest way

vagrant vector
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8 is 1

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8 is 1 green part

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16 is 2 green parts

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U want to find 1 green part to do your Pythagoras theorem with

sturdy lodge
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Ohh

vagrant vector
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@ashen dust don't be rude smh

sturdy lodge
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Now I got it

ashen dust
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uhm no i just think its funny ;-;

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sorry then

sturdy lodge
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And the Pythagoras

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Stuff

vagrant vector
sturdy lodge
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Yea so confusing

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Kind of

vagrant vector
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Yeah

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it's ok as long as u get it

sturdy lodge
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Can u make understand the Pythagoras

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Theorem

vagrant vector
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I can tell u what it does

sturdy lodge
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Like that in a consise way

vagrant vector
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Uhm

sturdy lodge
#

I never understand my teacher

vagrant vector
sturdy lodge
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Yea

vagrant vector
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<ABC is a right angle

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So

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when AB is squared

sturdy lodge
vagrant vector
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And added to BC²

sturdy lodge
#

This right

vagrant vector
sturdy lodge
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Ohh

vagrant vector
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Where AC is the hypotenuse length

sturdy lodge
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Ohh okay

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Then

vagrant vector
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In your question

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U have the hypotenuse

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So u want to find one of the other sides

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so u take the hypotenuse length and square it

sturdy lodge
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Yea there are two hypotenuse

vagrant vector
vagrant vector
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I mean in 1 triangle

vagrant vector
sturdy lodge
#

No I mean there are two right triangle

vagrant vector
sturdy lodge
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So two

vagrant vector
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Both are the same

sturdy lodge
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Hypotenuse

vagrant vector
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So just choose 1

sturdy lodge
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I got it

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So like this is it

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Are u here?

vagrant vector
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Ya

vagrant vector
sturdy lodge
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I mean the whole

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Pythagoras

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Stuff

vagrant vector
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Ya

sturdy lodge
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Okay

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Now next

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Problem

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@vagrant vector

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.close

final saddleBOT
#
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wind hawk
#

Hey

final saddleBOT
wind hawk
#

Can someone explain the range and domain of functions

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.close

final saddleBOT
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final saddleBOT
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barren orbit
#

Need help checking the continuity of this limit

barren orbit
#

I was taught that the first step is to make sure that f(x) at the 0 is defined

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However here it is undefined

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So this function should be non-continuous right?

minor nexus
#

heres what it looks like on desmos, so i guess not

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but i think it can be done by thinking about what happens as x is small

final tangle
#

ideas seem to be conflated here

minor nexus
#

if x is something like 0.01

your function is
0.01 ^ 1/0.01 = 0.01 ^ 100
Which is very close to zero

final tangle
#

continuity and limits are related,
the function not being defined at a certain value indicates some discontinuity there
but that doesn't necessarily mean the limit won't exist

final saddleBOT
#

@barren orbit Has your question been resolved?

barren orbit
#

I cant find the function

minor nexus
#

type floor

barren orbit
#

Oh wait

barren orbit
#

Because it probably does

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But the question was to examine the continuity of the function at x = 0

final tangle
#

then what was

Need help checking the continuity of this limit
about

barren orbit
#

Sorry if I was annoying šŸ˜”

final tangle
#

well yeh, if a function isn't defined somewhere, it isn't continuous there

barren orbit
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hallow cipher
#

check this out I got this function that describes the time it takes for an object to land when thrown at the speed of 30m/s on the angle x assuming no wind, or anything like that. how can I find the angle that gives the highest total distance?

hallow cipher
#

also what does f'(x) imply?

#

.close

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floral shadow
final saddleBOT
floral shadow
#

Did I do b right

#

If so how do I simplify tan^2 x +1=0

solar glade
#

,rcw 90

soft zealotBOT
lofty spade
#

2 positive quantities cannot add up to 0

still berry
# soft zealot

you made a calc mistake there (1-tan^2x+2) should be -tan^2x+3

floral shadow
#

can i find an asnwer with -tan^2x +3

still berry
#

yes you can

floral shadow
#

wait how

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the answers say pi/3

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2pi/3

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and 0 and 180

floral shadow
still berry
#

so x will be pi/3 or 2pi/3

floral shadow
#

oh got it

floral shadow
#

and rooting 3 is impoosible

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oh wait

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you multiple it all by root -1

still berry
floral shadow
#

yeah

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i get it now ty

final saddleBOT
#

@floral shadow Has your question been resolved?

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proper yoke
#

does anyone know how to solve this? "deside X from the matrix ... if A = ..."

final saddleBOT
#

@proper yoke Has your question been resolved?

severe canyon
#

You have $$A^T \left( X - B^T \right) = 7 \left( X - B^T \right)$$

soft zealotBOT
#

Alberto Z.

proper yoke
#

Yes

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Well the ^T is not just on the A

severe canyon
soft zealotBOT
#

Alberto Z.

proper yoke
#

Okay but is it not easier to just multiply the A in the parentheses and then do ^T?

severe canyon
#

Yes it's the same

proper yoke
#

So we have AX - (AB)^T

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On lhs

severe canyon
#

Yep

proper yoke
#

Okay so what do we do now?

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Do we multiply the 7 on rhs?

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X = (A -7I)^-1 - 7B^T + (AB)^T

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Is this correct?

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@severe canyon

severe canyon
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I don't think so

proper yoke
#

Okay let me do it like you started

proper yoke
final saddleBOT
#

@proper yoke Has your question been resolved?

final saddleBOT
#

@proper yoke Has your question been resolved?

proper yoke
#

.close

final saddleBOT
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final saddleBOT
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pure linden
final saddleBOT
half salmon
#

!status

final saddleBOT
#
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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
half salmon
#

If you set those linear equations equal to eachother what answer would you get out of it? Hint: where do they intersect?

pure linden
#

4,-4?

final saddleBOT
#

@pure linden Has your question been resolved?

craggy plank
#

@pure linden Are you still there?

final saddleBOT
#

@pure linden Has your question been resolved?

vital crag
#

the solution set is where the two lines intersect. count the squares

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honest egret
#

What is the inverse of the function f (x) = 3(x + 5)2 – 4, such that x ≤ –5?

honest egret
#

I'm having issues knowing what to do

#

,help

soft zealotBOT
#

A brief description and guide on how to use me was sent to your DMs!
Please use ,list to see a list of all my commands, and ,help cmd to get detailed help on a command!

soft zealotBOT
#

Victor Grignard

steady prairie
#

is this what you meant?

#

inverse of this?

honest egret
#

so yes

steady prairie
#

well , old method

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oh well wait

#

$y=3(x+5)^2-4$

soft zealotBOT
#

Victor Grignard

steady prairie
#

$y+4=3(x+5)^2$

soft zealotBOT
#

Victor Grignard

steady prairie
#

$(y+4)/3=(x+5)^2$

soft zealotBOT
#

Victor Grignard

steady prairie
#

root (y+4)/3 -5 =x

honest egret
steady prairie
#

so A option

steady prairie
#

you're asking that?

honest egret
steady prairie
#

because I want it to equal to x

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and i'm increasing the degree of x

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by opening that

honest egret
#

alr ok

#

its either c or d right?

steady prairie
#

I don't think so

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otherwise the roots would've existed as conjugates of each other

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its A

honest egret
#

why

steady prairie
#

$x^2-(9+5i)x+(25i+20)$

soft zealotBOT
#

Victor Grignard

steady prairie
#

sum of roots = -b/a

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product of roots = c/a

abstract walrus
#

Its D

steady prairie
#

in the quadratic represented by

abstract walrus
#

If 4-5i is a root

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Its implied that

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4+5i must also be a root

steady prairie
#

$ax^2+bx+c$

soft zealotBOT
#

Victor Grignard

honest egret
#

why is it d then

steady prairie
#

in this

abstract walrus
#

Bwcauzs

#

Sum of roots

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-b/a

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4+5i +4-5i +5

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13

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So -13

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If in A ther was +5ix it would also be correct

honest egret
#

because they cancel each other out?

abstract walrus
#

Since they dont need tk be conjugates if there are complex coefficients

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No

steady prairie
abstract walrus
#

If a equation has real coefficients

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Then complex roots are in conjigates

steady prairie
abstract walrus
#

So we get D

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But if in the first option

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There was a +5ix

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Instead of -5

steady prairie
#

ik

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ye

abstract walrus
#

Then thats correct

steady prairie
#

silly me

honest egret
#

okay

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would it be 1

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i.e C

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.close

final saddleBOT
#
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final saddleBOT
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jovial folio
final saddleBOT
jovial folio
#

i can only figure out (x-3)^2 + (y+1)^2

#

idk how to do the horizontal strech by 3 and about the y-axis

steady prairie
#

the equation is of an ellipse

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but the horizontal stretch thing

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I don't get it

jovial folio
#

oh

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yeah

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usually u dont encouter that so idk

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/do you know how to find a^2 and b^2

steady prairie
#

I think that's called the semi major axes

#

a is 4

jovial folio
#

would a still be 4

steady prairie
#

measured from 3 to 7

jovial folio
#

if its transformed? with the stretches

steady prairie
#

oh wait

jovial folio
#

and about the y axis

steady prairie
#

that's the original circle

jovial folio
#

it kinda tricks u up

#

giving the circle

steady prairie
#

no

jovial folio
#

yeah

steady prairie
#

I think it means 3 in each side

#

3 units each side

#

do you have the answer?

jovial folio
#

nope

steady prairie
#

so according to me , its 3 units each side horizontally and 2 units vertically

jovial folio
#

(x-3)^2/9 + (y-1)^2/b^2 = 1

#

this is what i got

#

a = 9 because horizontal stretch by 3

#

y - 1 because shifted up 2

steady prairie
jovial folio
#

idk what to do about the y axis tho

steady prairie
#

a is 7

#

4+3

jovial folio
#

ok

steady prairie
#

and b is 4+2

#

6

#

so the equation will (x-3)^2/49 + (y+1)^2/36 =1

jovial folio
#

hm

#

i see

#

thanks

steady prairie
#

DO check it if you can

#

because it's what I've interpreted from the statement

jovial folio
#

@steady prairie did u do the about the y axis?

#

that it asked for

#

cuz idk how to do that

#

usually u just multiple by -1

final saddleBOT
#

@jovial folio Has your question been resolved?

final saddleBOT
#

@jovial folio Has your question been resolved?

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red field
#

any ideas?

final saddleBOT
red field
#

nvm i just realizied that the answer is 4 cuz there are infinitly of these

#

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tranquil pine
#

Can someone help me on #28 here? I just recently closed a channel on this and I still don't get it. I now know cis = cosine theta + i sin theta but that still doesn't really help. I know we're supposed to be converting to (r, theta) form but I'm not sure how

loud sundial
#

imma just use $\cos \alpha +i \sin \alpha$ and $\cos \beta+i \sin \beta$ for convenience

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

since I assume the problem is with the trig parts

#

what do you get immediately upon multiplying these

tranquil pine
#

im not sure

#

why are you multiplhying them?

loud sundial
#

let $z_1=r_1 \text{cis} \alpha$ and $z_2=r_2 \text{cis} \beta$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

then you have $z_1=r_1 (\cos \alpha +i \sin \alpha)$ and similar for $z_2$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

so that gives you $$z_1 z_2 =r_1 r_2 (\cos \alpha +i \sin \alpha)(\cos \beta +i \sin \beta)$$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

which is why I asked you to multiply out $$(\cos \alpha +i \sin \alpha)(\cos \beta +i \sin \beta)$$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

Don't overcomplicate it out - ||it's the same as multiplying out smthn like (x+5)(x+7)||

tranquil pine
#

one sec lemme write this out

#

or type it out lol

#

$(\cos(\alpha) \cdot \cos(\beta)) + (\cos(\alpha) \cdot i sin(\beta)) + (i \sin(\alpha) \cdot \cos(\beta)) + (i \sin(\alpha) \cdot i \sin(\beta))$

soft zealotBOT
#

BlazeStorm81

tranquil pine
#

ts so complex lmao

loud sundial
#

imma just rewrite that a bit

#

$[\cos \alpha \cos \beta -\sin \alpha \sin \beta]+i[\cos \alpha \sin \beta+\sin \alpha \cos \beta]$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

Now you can apply your ||trig addition identities||

tranquil pine
#

lemme see which trig identity suits this

tranquil pine
loud sundial
#

yeah

tranquil pine
#

so is this $\cos(\alpha+\beta) + i \cos(\beta+\alpha)$

#

?

soft zealotBOT
#

BlazeStorm81

loud sundial
#

close but no cigar

#

check the second term again

tranquil pine
#

oh

#

so is this $\cos(\alpha+\beta) + i \sin(\beta+\alpha)$

soft zealotBOT
#

BlazeStorm81

tranquil pine
#

i think thats the correct version

loud sundial
#

āœ…

tranquil pine
#

okay awesome whats the next step

loud sundial
#

so now we've shown that given this

#

we have that $z_1 z_2 =r_1 r_2 \text{ cis} (\alpha+\beta)$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

all of these are just a direct application of this

tranquil pine
# loud sundial

so is the answer then just $8 \cdot cis(\frac{\pi}{2}+\frac{\pi}{4})$

soft zealotBOT
#

BlazeStorm81

loud sundial
#

yup

tranquil pine
#

wow okay

#

thank you for helping out

#

i think i get it now

#

.close

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loud sundial
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uneven light
final saddleBOT
uneven light
#

can someone walk me thru this idk where to start

minor nexus
#

i think it is asking you to find y, so we can untangle it by first integrating to find dy/dx, then integrating again to find y

#

||dont forget +C||

minor nexus
#

yep perfect

uneven light
#

where does the y'(0) come in tho

#

i'm confused about that

#

and y(0) = 1

minor nexus
#

well, when you first integrate, you get something, +c

#

y'(x) = dy/dx

#

so you can find out what c is with that information

uneven light
#

i see

#

so when i get that integral that will be y'

#

and then for x i put 0

minor nexus
#

yep

uneven light
minor nexus
#

yep, i like that

uneven light
#

do i need to integrate asgain

minor nexus
#

we need to find y in terms of x

#

so yeah

uneven light
#

gotcha

#

y(0) = 1 sooo let me plug it in

minor nexus
#

not 100% agreed with your integration

#

i think you factorised -2 out of the integrql, but didnt do it for the other term

uneven light
#

wat

#

would the 2 just become x

#

not 2x

#

idk i forget

minor nexus
#

i wouldnt recommend factorising from line 2

#

you can integrate directly

uneven light
#

kay

#

so it would just be 2e^-x + 2x

minor nexus
#

||+c||

uneven light
#

yes ofc but otherwise those numbers are right?

minor nexus
#

yep, youre correct, good job

uneven light
minor nexus
#

yep, i think youre good

#

well done

uneven light
#

tysm for the help

#

been stuck on this question for a little bit

#

so its a relief

#

i appreciate you

#

.close

final saddleBOT
#
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minor nexus
#

no problem

final saddleBOT
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tranquil pine
#

can someone explain me how iz z^2 in x^2 and y^2 in the brackets?

silver hare
#

ok expand the top line

tranquil pine
#

moment

silver hare
#

?

tranquil pine
#

I dont get how the author wrote this problem for moment inertia

#

I dont understand either

silver hare
#

so whats ur question

tranquil pine
#

how is z^2 in x^2 and y^2 bracket

#

I dont get it

#

its +z^2

#

I marked with blue line the issue im stuck with

#

.close

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gritty temple
final saddleBOT
gritty temple
#

how can you tell with this one using the right hand rule

#

i cant tell since the curl seems to go in two different directions

#

(vector caclulus question)

magic sparrow
#

You can compute the cross product directly I think

#

it is confusing me aswell, it seems the normal in Q1/2 is in the opposite direction as in Q3/4

gritty temple
#

yeah its strange unlike anything ive seen before

magic sparrow
#

Maybe it isn't even asking you about the normal vector yet

#

in a right-hand coordinate system the z-axis points out of the page

#

maybe part (i) isn't even about the vector field yet

#

Can you show the other parts

gritty temple
#

sure

#

im only on part ii)

magic sparrow
#

This isn't a test right?

gritty temple
#

what do u mean

#

its homework questions

magic sparrow
#

Just asked because of the points (3) and stuff

gritty temple
#

ah

magic sparrow
#

Well anyways for part (i) I think it's just outward

gritty temple
#

what's the explaination for that?

magic sparrow
#

because it's a right hand coordinate system

gritty temple
#

yeah okay i get that then just the normal hand position

#

i thought it was asking about the curl hand position thing

final saddleBOT
#

@gritty temple Has your question been resolved?

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paper lodge
#

I need help with this problem. The way I setup is 40u''+94u'+120u=0 and u(0) = 5/12 ft, u'(0) = 4 ft/s. Is that wrong? Im missing the answer

paper lodge
#

<@&286206848099549185>

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#

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stiff belfry
#

it is wrong

final saddleBOT
#

@paper lodge Has your question been resolved?

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bright adder
#

Hello, I am trying to understand how to interpret eigenvalues. I did my work via matlab and was quite confused by the results i got.

royal gust
#

Why were you confused by your results?

bright adder
#

The results of the last row, decreases after the 5th year, and then increases at year 10. Also I'm trying to understand steady state of eigenvalues and eigenvectors, and while doing so I don't know if my explanation or understanding is correct based on the results

#

I'm wondering if I'm doing this correctly. Year 3 = A^3 * S, Year 5 = A^5 * S, Year 10 = A^10 * S right?

royal gust
#

Ye

bright adder
#

the eigenvalues i got were lambda = 1, 0.57192, 0.77807 through Matlab. And now I am struggling to interpret the eigenvectors and what the values are supposed to mean.

final saddleBOT
#

@bright adder Has your question been resolved?

bright adder
#

<@&286206848099549185>

#

I guess my question is: How do you interpret the value that has decreased and then increased exponentially?

royal gust
#

Consider the eigenvalue 1.
It comes with an eigenvector. I'll just call that v, right now.

This vector satisfies the following:
Av = 1v

#

This tells us something pretty important:
If you take anything in span(v), then A doesn't change it. This is a steady state.

bright adder
#

Lambda = 1; eigenvector doesn't change. Does the eigenvalue always have to be 1 for a steady state?

#

And is steady state the same as a stable eigenvector?

royal gust
#

Well, let's look at the eigenvalue 0.57.
This has an eigenvector, I'll now refer to this as v.

This vector satisfies the following:
Av = 0.57v

#

When A acts on this vector, the vector returns in the same direction, but decayed

#

I suppose in the context of this question, the three companies will fail, if their market share forms a vector in span(v)

bright adder
#

Would that also mean the samething for the eigenvalue of 0.778

royal gust
#

Indeed. They'll fail, but a bit slower.

bright adder
#

So like in this context, eigenvalue specifically helps determine value of their shares over time?

royal gust
#

If A doesn't change v's direction, v is an eigenvector of A.
A can still change v's magnitude. The factor by which v's magnitude is changed is v's eigenvalue.

#

In this case, eigenvalue represents an increase/decrease to all three shares

bright adder
#

if i'm understanding correctly, eigenvalue = rate of increase/decrease of the shares right?

#

and then if the eigenvalue is 1, it's steady

#

Is it the same as saying stable?

royal gust
#

It all comes together with:
Av = (lambda)v

Hopefully you've seen this equation before

#

If v is an eigenvector of A, then A acts like a constant multiplier to v.

#

I suspect the question is just looking for the eigenvector with eigenvalue 1

#

Because that's when the market has no movement

bright adder
#

so then the eigenvector kind of predicts how the shares will redistribute overtime to the three companies right?

royal gust
#

If you plug an eigenvector into A, then you'll get back the exact same vector, except multipled by some constant

#

In a sense, this is the "easiest to understand" action A can possibly take

bright adder
#

ty for the help

#

sorry i've been struggling with this for the last few days and every explanation still confuses me

#

If I understand this, the eigenvector has a specific value associated which is the eigenvalue. When eigenvector multiplied by A, then it will be equal to some constant * eigenvector.

royal gust
#

Yeah, exactly

#

Worth noting that most vectors get "turned" by A. Eigenvectors are special because they maintain their direction after A.

#

It's worth thinking of a few simple examples, I'll throw one at you:
Consider the linear transformation in R2 that flips vectors vertically. For example, (1,1) becomes (1,-1)

#

What are some eigenvectors of this?

bright adder
#

gimme one second to write this down

#

eigenvalues = -1.41, 1.41; eigenvectors = (2.41, 2.41) for lambda = 1.41

royal gust
#

All this transformation does is flip vectors vertically. It just multiplies the second component by -1

#

Are any vectors unchanged by this action?

bright adder
#

No?

royal gust
#

Consider (1,0)

#

If I flip that vertically, then I get back (1,0)

#

So (1,0) is an eigenvector, and it has an eigenvalue 1.

bright adder
#

So instead of 1 row with 2 columns, the flip becomes 2 rows 1 column right?

royal gust
#

,w vector (1,0)

royal gust
#

I mean geometrically, over the x-axis

#

,w vector (1,-1) and (1,1)

royal gust
#

So yellow would turn into blue, after our transformation

bright adder
#

And A tells you how that is done while the eigenvalue tells you whether or not it's longer or shorter than the span?

royal gust
#

A is the transformation itself. We could find a matrix for it, but it's easy enough to describe without a matrix representation, I think

#

(1,0) is an eigenvector. When you take (1,0) and flip it over the x-axis, it stays exactly where it is.

#

Because it doesn't grow or shrink, the eigenvalue is 1.

#

Are there any other eigenvectors?

bright adder
#

No

royal gust
#

Note that anything on the x-axis counts as an eigenvector

bright adder
#

is it because it's in the same direction?

royal gust
#

But we normally group them and refer to them with their span

#

So (1,0) refers to all of these

#

,w vector (0,1) and (0,-1)

royal gust
#

So if we plug blue in, we get yellow back. Blue and yellow are "in the same direction", just opposite. This is an eigenvector too.

#

(0,1) is an eigenvector with eigenvalue -1

bright adder
#

ty i think im starting to understand now

#

i just need to digest the info a little more

#

i appreciate the time you took to help me šŸ˜„

royal gust
#

Np. Feel free to ask if you have anything else!

final saddleBOT
#

@bright adder Has your question been resolved?

#
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rotund glen
final saddleBOT
rotund glen
#

am i able to say yes?

#

for that last part

#

i got these graphs

#

so i can see it gradually getting closer

#

<@&286206848099549185>

tiny gorge
#

the error will go to zero as n->infinity, but i assume you need to prove this

rotund glen
#

how would i go about doing that @tiny gorge ?

#

we have these notes

tiny gorge
#

offhand i'd think that uniform continuity and a bound on the derivative of sine would be helpful

rotund glen
#

shit okay

#

do you think the question was asking for a formal proof?

#

i am not sure how to go about the proof tbbh

tiny gorge
rotund glen
#

numerical analysis

#

i think based on the question tbh, its asking us to look at the matlab graphs n see how the trend would continue

#

which we can say it will go to zero

#

but feel free to disagree ofc

tiny gorge
#

do they ask you to do other proofs in this class? if not then yea, i'd guess they just want you to try making plots for various values of n and see from the graphs that the approximation error is going to zero

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#

@rotund glen Has your question been resolved?

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hybrid tide
#

MN is equal to half the length of XZ

final saddleBOT
hybrid tide
#

?

craggy plank
final saddleBOT
# hybrid tide MN is equal to half the length of XZ
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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
hybrid tide
#

2

craggy plank
hybrid tide
craggy plank
#

Which is longer? MN or XZ?

#

@hybrid tide

hybrid tide
#

XZ MN is half the length of XZ

craggy plank
#

Translate it in English

#

Like
x=2y
x has twice numbers of apples than y do

hybrid tide
#

U have to use the midsegment theorem here

craggy plank
#

Ik

#

But I suggest you think twice about your first equation

hybrid tide
#

But isn't MN supposed to be 1/2 of XZ?

craggy plank
#

yes it is

#

That’s why I told you to look at your equation and translate it

hybrid tide
#

I don't get what u mean by translate

craggy plank
#

There’s a small but fatal mistake

#

Well

#

What you wrote in the equation is XZ is 1/2 of MN

hybrid tide
#

MN is 2x+1

#

XZ is 5x-4

#

1/2(2x+1)=(5x-4)

#

I don't get what I'm doing wrong

craggy plank
#

Lemme translate it for you

#

When you divide MN into two parts, you’ll get XZ

hybrid tide
#

Yes

craggy plank
#

What you want is
XZ is twice longer than MN

hybrid tide
#

Yes

craggy plank
#

The first one is what you wrote

hybrid tide
#

I'm listening

craggy plank
#

Have you found your mistakes?

hybrid tide
#

Nope šŸ˜‚

craggy plank
#

..

craggy plank
hybrid tide
#

Oh

#

Alr I get it

#

Thx šŸ™

#

.close

final saddleBOT
#
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warm python
#

$a_n=\frac{\left(2n+1\right)}{\sum_{i=1}^nn^2}$, find $\sum_{i=1}^{20}a_i$

soft zealotBOT
#

Why am. I here

warm python
#

so I'm guessing I expand and simply use partial fractions to decompose the second part?

#

or is there a better way>

#

which would be

ocean lintel
#

You can pfd that, sure
Assuming it's sum of the i^2

warm python
#

yeah

#

but is there any better way

ocean lintel
#

Then probably express it using the harmonic sequence

ocean lintel
scarlet sequoia
#

this really just looks like 'do you know the formula for sum(k^2)'

#

and 'do you know how to pfd'

#

and finally 'do you know telescoping'

ocean lintel
#

Oh yeah you do get some telescoping

warm python
#

so $\sum_{n=1}^{20}\frac{12}{\left(n+1\right)\left(2n+1\right)}+\frac{6}{\left(\left(n\right)\right)\left(n+1\right)\left(2n+1\right)}$

soft zealotBOT
#

Why am. I here

warm python
#

ah, ok. This is. going to take a while, but I think I can do it from here. Thanks

#

.lcose

#

.close

final saddleBOT
#
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magic sparrow
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.lcose

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.lreopen

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.llosec

magic sparrow
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.laceolse

ocean lintel
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We're all children aren't we

scarlet sequoia
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when you get 16 year old, the only thing that ages is your body

magic sparrow
robust mulch
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i am older than you

ocean lintel
magic sparrow
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are u

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gookman is 20?!??

scarlet sequoia
ocean lintel
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Who's gookman

magic sparrow
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@robust mulch

robust mulch
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gookman

scarlet sequoia
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i said sup_years(the rest aging) <= 16

final saddleBOT
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covert folio
final saddleBOT
covert folio
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hi

magic sparrow
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Hello

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!status

final saddleBOT
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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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
covert folio
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how do i do part b?

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i dont know where to begin

magic sparrow
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use properties of square roots that you know

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rationalize denominators

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make common denominators

covert folio
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so i make it 1 big fraction first?

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by multiplying the denominators together?

magic sparrow
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do all kinds of simplification

covert folio
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.close

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final saddleBOT
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lime cloak
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Hi, i wonder where i made mistake

final saddleBOT
lime cloak
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The text of the exercise is "determine the derivatives of the following functions"

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On the left is solution in book

desert mantle
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they made a mistake

lime cloak
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Thanks

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. close

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.close

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tranquil pine
final saddleBOT
tranquil pine
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im just confused of

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x < 0 and x <= -2 intersects

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so

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how am i supposed to make it

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do i take the lowest one

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e.g x <=-2, x> -2

craggy plank
tranquil pine
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??

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u need translate?

craggy plank
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I’m just watching

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Ignore me

tranquil pine
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help me :(

craggy plank
tranquil pine
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why

craggy plank
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I’ve solved a lot of problems today

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Kinda need some rest šŸ˜„

tranquil pine
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same

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i solve a lot everyday

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ok u can rest here

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;)

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@tranquil pine Has your question been resolved?

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lavish crescent
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how do i solve question 1 (a)?

final saddleBOT
tranquil pine
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what have you tried

lavish crescent
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supplementary relationships

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so cos 140 = sin40

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i think

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oh wait nvm i got it

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.close

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lilac estuary
#

Consider the inner product space R^3 where vector addition and scalar multiplicationa re defined in the usual way and the inner product on R^3 Ɨ R^3is the standard dot product.
Let S : R^3 → R^3 describe an orthogonal reflection in the plane P, where P is
described by the Cartesian equation z = 0.

(a) Find the matrix AS that represents S with respect to the standard ordered basis
{e1, e2, e3} of R^3

lilac estuary
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I know I have to find the effect of S on e1, e2 and e3 and then the entries of my matrix will be the transformed standard vectors but I have no clue on what the effect is

junior token
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have you tried drawing a picture of the reflection?

final saddleBOT
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@lilac estuary Has your question been resolved?

lilac estuary
junior token
lilac estuary
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how did you get that?

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orthogonal reflcetion in the plan P where P is described by z=0

junior token
lilac estuary
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yes so how come the z is reflected if the prthgonal reflection is in the x and y plane

junior token
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the things on the mirror aren’t reflected

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but everything else is

lilac estuary
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alright I get it

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it's an orthogonal reflection with respect to P

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therefore As=(e1,e2,-e3) with ei the standard basis of R^3

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i=1,2,3

junior token
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Yes

lilac estuary
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ty

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.close

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final saddleBOT
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sour torrent
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I’m really struggling with this

final saddleBOT
sour torrent
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I am doing old exams so I have the solution but it does not make much sense to me

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Any explanation is appreciated

next onyx
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pythagoras right?

sour torrent
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No

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This is multi variable Calc so I’m doing triple integrals but the integral boundaries are the main issue

scarlet sequoia
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this is spheric coordinates

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r = sqrt(x^2+y^2+z^2)

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x = rcos(theta)cos(phi)

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y = rcos(theta)sin(phi)

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z = rsin(theta)

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theta goes from 0 to 2pi

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phi goes from 0 to pi

lyric summit
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spherical coords must be applied with modification of one of angles, you will need to use arc cosine

sour torrent
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Here is the solution btw

lyric summit
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yoru solution is based on cylindrical, bu ti wud use spherical

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precisely

sour torrent
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I’m not gonna lie I’m kinda lost

lyric summit
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that can be useful:

sour torrent
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Okay that makes sense

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I get it a bit more

lyric summit
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-pi/2 < phi< arc cos ( sqr ( a^2 - b^2 ) )

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but i said, i wud use spherical coords

sour torrent
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Can you explain how you would do this step by step?

lyric summit
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hmm eng is not my native one, it is hard fo rme to use beauty words to descrieb it, i just can see it at once

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theta angle is walkign around from 0 to 2pi

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that is, i wud say flat angle

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if you stand on z axis and you look at the flor

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you can see circle

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btw, i wud change y < b into z < b

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since voluem wil be the same

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and phi angle

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i stay on vertz of x axs

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and then i see this photo i gave you here