#help-26

1 messages · Page 220 of 1

loud oasis
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so the thing is that there are always two angles between any two lines, which are supplementary, and also always two angles between any two planes, which are supplementary

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so if you find one of the two angles between the two normal vectors then you find one of the two angles between the planes

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and the other one is just the supplement of that

shut obsidian
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Something like this

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Imagine tilting both of the arrows at the same time to the left

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This is what I was describing

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Both are offset by 90° so they will lie flat in the planes at the same time

heavy timber
loud oasis
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i didn't claim they're equal, i said they are supplementary

heavy timber
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oh

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like 180 - x = y

loud oasis
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but the point is that there is a pair of supplementary angles between the two planes, and also a pair of supplementary angles between the normal vectors

heavy timber
#

may i ask for the defination of the word supplementary

loud oasis
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adds up to 180 degrees

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i have taken the liberty to draw the full set of angles here:

heavy timber
#

so thats why we use doty product with | | to evaluate the angle

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lovely.

loud oasis
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we would use absolute value if you want to only get the acute angle, yes

heavy timber
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well thats one part the teacher explained that we always use the smaller one. we can use the other one but we dont.

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well yes everything makes sense now

heavy timber
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ty cloud and kepe.

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.close

topaz sinewBOT
#
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topaz sinewBOT
#
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proud flare
#

Part b)

topaz sinewBOT
proud flare
#

How do i integrate 1/(x-1)^2

mystic grove
#

man

proud flare
restive inlet
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(reverse) power rule (with trivial application of chain rule)

mystic grove
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think about can you make x+1 as a single term?

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and integrate it wrt that term?

mystic grove
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assum x+1 = a

proud flare
mystic grove
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integrate it for a^-2 da

proud flare
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Why

mystic grove
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you could do it with as x+1

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its easier you could do it normally to

restive inlet
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if you're struggling with what you currently have
doing a substitution can get you something you may be more comfortable with

mystic grove
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doom um no offense but do you have an general idea abt integration? the question in part a looks like a algebra one

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are you doing precalc rn?

proud flare
mystic grove
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leave it for later

restive inlet
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partial fractions is a technique in integration

mystic grove
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there are a few rules you need to know

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the person who made it probably included it by mistake

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dw about it

proud flare
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This is my work

restive inlet
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the two parts have a direct link

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there is no mistake in the question setup

mystic grove
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mb

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sorry

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it becomes ln2x+3/x-1

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you have to divide it ?

drifting swift
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ln( (2x+3)/(x-1) )

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none of these are droppable

mystic grove
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im sorry

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Im not used to typing yet

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I normally do it on paper

restive inlet
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no real need to combine them yet

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but anyway, lets focus on
$$\int_2^a \frac{1}{(x-1)^2}\dd{x}$$

obtuse salmon
#

Dx

thorny flameBOT
#

ραμOmeganato5

restive inlet
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would you know how to integrate something like
$$\int \frac{1}{x^2} \dd{x}$$

thorny flameBOT
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ραμOmeganato5

proud flare
restive inlet
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no, that'd be incorrect

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are you familiar with the power rule for derivatives?

proud flare
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kinda

sharp pagoda
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try thinking inversely

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what derivated would you get 1/x^2

proud flare
sharp pagoda
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no

restive inlet
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no

sharp pagoda
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oh yea

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yea wrong direction

mystic grove
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doom

proud flare
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Yes

mystic grove
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do you know what the derivative of x^n is?

proud flare
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Yes

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nx^n-1

mystic grove
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in the question what do you diffrentiate to get 1/(x-1)^2?

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basically d/da (A) = 1/(x-1)^2 solve for a

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hello::

proud flare
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Is it this

restive inlet
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yes

mystic grove
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yes

sharp pagoda
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huh

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how is that a yes

mystic grove
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+1 in the power

sharp pagoda
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i mean yea but it skipped some steps but whatever

mystic grove
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ok doom since you are given a and 2 as your limits you can subsitute them

sharp pagoda
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no you cannot

mystic grove
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why not ?

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Im getting the ans?

sharp pagoda
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you cant just integrate 1/(x-1)^2

mystic grove
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why not 🙁

sharp pagoda
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you need u substitution for x-1

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1/(x-1)^2 != 1/x^2

mystic grove
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man

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he did it directly

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it isnt a big deal

sharp pagoda
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it is

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the bounds arent the same

mystic grove
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I swear when ever i type I keep missing few words

mystic grove
restive inlet
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if you keep the same bounds there is no issue here

mystic grove
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you telling me

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if I say x-1 = a and integrate a from 2 to 3 I cant use the same bounds????

sharp pagoda
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the bounds are 1 lower

restive inlet
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the application of chain rule is simple enough here that you don't need to explicitly go through that whole substitution process

mystic grove
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I would just use that rule for multipication

restive inlet
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there was no sub, there is no need to change the bounds

proud flare
sharp pagoda
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I might be wrong tho

proud flare
mystic grove
restive inlet
mystic grove
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now just simplify into ln d and c

sharp pagoda
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yea

proud flare
sharp pagoda
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ln(a) + ln(b) = ln(ab)

restive inlet
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combine logs with sum/difference → product/quotient laws

proud flare
sharp pagoda
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ln(a) - ln(b) = ln(a/b)

obtuse salmon
sharp pagoda
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ok sry then i was dumb

obtuse salmon
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Np

proud flare
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Is it good

restive inlet
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looks good

mystic grove
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yes

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correct

proud flare
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Wait but in the question it says c + ln d and i have that extra +1

mystic grove
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it is included in c

restive inlet
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the whole -1/(a-1) + 1 will be the c

proud flare
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Okay solved then tysm guys

#

.close

topaz sinewBOT
#
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topaz sinewBOT
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simple canopy
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im stuck

topaz sinewBOT
drifting swift
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i think you have come here with this question before and we concluded you didn't know anything about complex numbers

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have you learned anything about those since then?

simple canopy
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how do u even remember all that 😭

simple canopy
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a little

drifting swift
simple canopy
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i tried replacing i with +1 and then got 2 in the denominator then 2 got cancelled and i got left with 3i

drifting swift
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i isn't 1

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so no

simple canopy
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wait

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so i = -1 ?

drifting swift
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no

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i is i

simple canopy
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oh

drifting swift
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it isn't a real number

simple canopy
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so what should i do

drifting swift
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ok so let's maybe go over some basics

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do you know how to add or subtract complex numbers

simple canopy
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yes

drifting swift
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and multiply?

simple canopy
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um

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not sure

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maybe

drifting swift
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ok let's set this one aside for a bit

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cause you do need to know how to multiply complex numbers before learning to divide them

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i would like you to try your hand at multiplying these complex numbers:

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(3+2i) * (7+i)

simple canopy
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alr

drifting swift
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[we will get back to your original question later! this one is simply to check what you do and don't know]

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i am also gonna disappear in 20 min due to an appointment so would like to make it quick if we can.

simple canopy
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alr

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im stuck on 21+17i+2i^2

drifting swift
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so far so good, now remember i^2 = -1.

simple canopy
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oh yes

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u are right

drifting swift
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complete the last simplification step

simple canopy
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5 is the ans ?

drifting swift
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how did that all get down to just 5

simple canopy
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oh no wai

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im getting 2 now

drifting swift
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just 2??

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show me your work.

simple canopy
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alr

drifting swift
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i didn't name myself after her, no.

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@simple canopy btw when i say show your work i mean show your work

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i don't mean go and redo the thing again and hope the answer will stick this time

simple canopy
drifting swift
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i = 19-17

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wtf is this

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i isn't an unknown to solve for, it is the imaginary unit.

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19+17i is your final answer

neon iron
drifting swift
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no

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i isn't undefined

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i is i

neon iron
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√-1?

simple canopy
drifting swift
simple canopy
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so i was doing it right

drifting swift
neon iron
drifting swift
#

anyway here. practice MULTIPLYING complex numbers. then watch this vid. https://youtu.be/EfRRpVB62Ko

This algebra video tutorial explains how to divide complex numbers as well as simplifying complex numbers in the process. It includes dividing complex numbers with square roots and radicals as well as dividing complex numbers in standard form. This video contains plenty of examples and practice problems.

Complex Numbers - Free Formula Sheet: ...

▶ Play video
simple canopy
#

i didnt know that we dont have to further solve it

drifting swift
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that view is very unhelpful when working with complex numbers.

simple canopy
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thanks ann u are a huge help everytime

nova grail
thorny flameBOT
#

Kaladin.

nova grail
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btw

simple canopy
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so i is just i right ?

nova grail
#

yes

neon iron
drifting swift
neon iron
simple canopy
drifting swift
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well the first half of the question just asks you to work out a itself

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and name its real part and imaginary part

simple canopy
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whats a conjugate ?

drifting swift
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i.e. to get the conjugate of a complex number you flip only its imaginary component

simple canopy
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the opposite ?

neon iron
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I meant that i is a whole new concept instead of just real numbers and that also means that "we can't put it in a real value " that's what I meant but it's just obvious

drifting swift
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no.

the conjugate of 4+20i is 4-20i
the opposite of 4+20i is -4-20i

drifting swift
drifting swift
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be careful with SPECIFICALLY the phrase "yeah right". like those words in that order.

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ppl may misunderstand you.

drifting swift
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ive given op instructions on what to do next on his own

neon iron
simple canopy
#

im closing the channel now guys thank u all

drifting swift
#

OP means original poster

neon iron
drifting swift
#

that's ouchyaar in this case

simple canopy
#

.close

topaz sinewBOT
#
Channel closed

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topaz sinewBOT
#
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real kiln
#

I've been given the following f(f(x)-2y) = 2x-3y+f(f(y)-x) for x,y real. I've been able to prove bijectivity of f but nothing more comes to my mind, i don't want the answer, only a path to continue searching. Thank you

exotic dome
#

The question is to prove f is bijective ? Do we know if it’s continuous ?

real kiln
#

no the question is to find all functions f which respect this equation

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it's not given continuous but it may be

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Also i saw that f(x) = x + b for some constant b is a valid solution

exotic dome
#

How did you prove bijective

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@real kiln

thorny flameBOT
#

Kawachi
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

exotic dome
#

Ok

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Pas mal

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Tu peux t’arranger pour simplifier l’expression en prenant 2x -3y = 0

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Tu choisis un y tel que l’égalité au dessus marche

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Ca te simplifie le truc

real kiln
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oui ca va donner un truc que je pourrais simplifier dans l'équation initiale

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mais ca donne f(3/2x) = f(x) - 1/2

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et avec ça je n'ai pas su avancer

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Let $P(x,y)$, l'assertion donnée.
Let $t \in R $ $$P(f(y)-t,y) \equiv f(f(f(y)-t)-2y)=2f(y)-2t-3y+f(t)$$
$$P(2y, f(y)-t) \equiv f(f(2y)-2f(y)+2t)) = 4y-3f(y)+3t+f(f(f(y)-t)-2y)$$
There's an equal term, so we get $$2f(y)-2t-3y+f(t) = f(f(2y)-2f(y)+2t)) - 4y+3f(y)-3t$$
$$\Leftrightarrow f(f(2y)-2f(y)+2t)) = y+f(t)-f(y)+t$$
taking $y=t$ : $$f(f(2y)-2f(y)+2y)) = 2y$$
So, $f$ est surjective.

Suppose $u\neq v$ such that $f(u) = f(v) $ then
$$P(u,y) = P(v,y)$$
$$\Leftrightarrow 2u+f(f(y)-u)=2v+f(f(y)-v)$$
by surjectiviy, there exists $y$ such that $f(y) = u+v$
We get $$2u+f(v)=2v+f(u) \implies u = v$$
So f is bijective

thorny flameBOT
#

Kawachi
Compile Error! Click the errors reaction for more information.
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real kiln
#

<@&286206848099549185>

ruby cove
real kiln
#

I'm asking for solving in f the functional equation f(f(x)-2y) = 2x-3y+f(f(y)-x) for x,y real which I've proved bijectivity

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is it even the good channel to post this ?

exotic dome
#

If f is continuous the solution is easy. But are you sure continuity is not a given ?

real kiln
#

yes i'm sure it's not given

exotic dome
#

Then perhaps we should prove it separately

real kiln
#

and showing continuity is difficult or impossible so there has to be another way

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uh showing continuity ?

exotic dome
#

Tu peux screenshot l’énoncé ?

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Je suis juste curieux

real kiln
outer portal
real kiln
#

Dm the bot ?

outer portal
#

that means to message the texit bot, here

#

try sending ,help

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or ,preamble

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dont do it directly on this channel though, fixing the \R isnt that related to the problem

real kiln
#

ok but still, nobody has ideas ?

outer portal
#

instead I got f(3t) - f(2t) = t, or f(3/2 x) = f(x) + x/2

real kiln
#

my mistake what you got is true i flipped the sign

outer portal
#

you can then rewrite it to look like this
so we know that, for powers of 3/2, the slope between the points is always 1

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from this you can try out f(x) = x + g(x)

real kiln
#

yes yes it gives $g(\frac{3t}{2})=g(t)$ for all real $t$ but sadly without continuity you go nowhere

thorny flameBOT
#

Kawachi

outer portal
#

I also got g(g(x) - x) = g(g(x))

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g(x) does not need to be injective and does not need to be surjective, since g(x) = 0 is a valid solution (since f(x) = x is a valid solution)

real kiln
#

yupp i totally agree and if you try f(x) = x + b is valid

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so we're left either to prove g is constant which i think is impossible

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otherwise prove f(x) = x + t in another way

topaz sinewBOT
#

@real kiln Has your question been resolved?

topaz sinewBOT
#

@real kiln Has your question been resolved?

topaz sinewBOT
#

@real kiln Has your question been resolved?

mint crescent
#

I think considering ||P(f(x),x)||, ||P(x,0)||, ||P(f(0)-x,0)|| might work

real kiln
#

It may helps but i don't know how

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if i state f(0) = a i got

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  1. $$f(f(f(x)-2x) = 2f(x)-3x+a$$
thorny flameBOT
#

Kawachi

real kiln
#
  1. $$f(f(x)) = 2x+ f(a-x)$$
thorny flameBOT
#

Kawachi

real kiln
#

3.$$f(f(a-x) = 2a-2x + f(x) $$

thorny flameBOT
#

Kawachi

real kiln
#

oh man i think you got this

#

Oh yeay it was clever

#

i'm able to solve this now thanks to you

#

.close

topaz sinewBOT
#
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limber halo
#

Can I have a starting point for this problem?

mystic grove
limber halo
#

Ok

limber halo
mystic grove
#

can you try showing that H lies on MC and BN?

limber halo
#

Ok I’ll try that thanks for the hint

#

.close

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#
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mystic grove
#

wait

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hold on

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Im DUMB

#

just prove p1=p2 powers of each

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then the chord is radical axis

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@limber halo

topaz sinewBOT
#
Available help channel!

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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
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eternal sierra
topaz sinewBOT
eternal sierra
#

i got
f(x) = cos(arctanx - arccot x)

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which i wrote as sin(pi/2+arctanx-arccotx) = sin(2arctanx)

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but i seem to be missing a (-) sign somewhere?

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cause my integration is supposed to give -arctanx+c

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but its giving arctanx

tight nexus
#

What's the question?

eternal sierra
#

find y(-sqrt(3))

tight nexus
#

Surely you can just write

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$y = \frac{1}{2} \arcsin{f(x)} + C$

thorny flameBOT
#

Miyagi

eternal sierra
#

ok sure

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but that still dosent help with the - sign

craggy marsh
tight nexus
#

I got $f(x) = \frac{2x}{1 + x^2}$

thorny flameBOT
#

Miyagi

eternal sierra
#

🤔

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thats def wrong

tight nexus
#

How

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Look

eternal sierra
#

f(x) = -tan^-1 x + c

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according to the solution

tight nexus
#

In the book?

eternal sierra
tight nexus
#

What do you mean mate

eternal sierra
#

yeah that is correct

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now put it in the differential eqn

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and tell what u get pls

tight nexus
#

How about you do it yourself

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I already have my answer but you're the one doing the question

eternal sierra
#

then why even message

eternal sierra
coral wraith
#

sure, but since you're the one who posted the question and are going to have to do the working out anyways, you might as well get on with it

coral wraith
#

Then show it here

eternal sierra
#

and i had an error in one of the steps

eternal sierra
#

what more do u want

tight nexus
#

That working is not going to help you

coral wraith
eternal sierra
tight nexus
#

Because its gibberish

eternal sierra
coral wraith
#

"Okay, but I did put this into the DE, and still had this problem - [PROBLEM]; any hints?"

eternal sierra
coral wraith
#

Verbs without a subject in English come off as instructions, which in certain settings are rude, to say the least, if not properly used

tight nexus
#

$f(x) = \frac{2x}{1+x^2} \
\frac{dy}{dx} = \frac{1}{2} \frac{d}{dx} \sin^{-1} {f(x)}$

eternal sierra
tight nexus
#

You just have to solve for y mate

eternal sierra
thorny flameBOT
#

Miyagi

tight nexus
#

To be honest I don't know where they got that negative sign from

eternal sierra
#

are u serious

#

why not say that at the start

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rather than waste my time..

coral wraith
#

I'd like to point out that this isn't even much of a DE, since you can just integrate this

eternal sierra
#

that was already pointed out before

#

.close

topaz sinewBOT
#
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topaz sinewBOT
#
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Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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sharp meteor
#

why is it specifically x-a, is it because were shifting the graph p(x) by a?

sharp meteor
#

cause of the approximation about 0, it makes sense

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but say now we do approximation about p(x-a) what does that change?

loud oasis
#

approximating f(x) around a is the same as approximating f(x-a) around 0

sharp meteor
#

oh so were just shifting the grpah back to the orgin

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then carrying it out

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Ohh i see

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why is it x-a and not x+a ?

topaz onyx
#

This is not your thread

#

lmao

sharp meteor
#

how would the eq look liff

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it would be f(x-a) = ...

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but have f(a)

#

?

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for the derivative points

topaz onyx
loud oasis
#

actually let's redo it. so let's define $g(x) = f(x + a)$. so $g(0) = f(a)$ and so on. then
[ g(x) \approx g(0) + g'(0)(x) + \frac{g''(0)}{2}x^2 ]
then since $f(x) = g(x-a)$ we have
[ f(x) \approx g(0) + g'(0) (x-a) + \frac{g''(0)}{2}(x-a)^2 ]
then replacing $g(0) = f(a)$, $g'(0) = f'(a)$, $g''(0) = f''(a)$:
[ f(x) \approx f(a) + f'(a) (x-a) + \frac{f''(a)}{2}(x-a)^2 ]

thorny flameBOT
#

κλαουντ ☁ (cloud)

sharp meteor
#

oh wait

#

i see

topaz onyx
#

The idea behind taylor series is that a function $f$ with infinitely many non-zero derivatives (for example, trigonometric functions) can be represented as the sum of an infinite polynomial,

$$f(x) = \sum_{n = 0}^{\infty} \frac{f^{(n)}(a)}{n!} \cdot (x - a)^n$$

where $f^{(n)}$ is the nth derivative of the function $f$.

We take the first 3 terms of this series to reach the approximation you're seeing

sharp meteor
#

ty

#

yea, what i was confused with was when it wasnt centred at 0

#

but we want to always try and shift it

#

so that it is

#

?

topaz onyx
#

Oh sorry, I forgot to do x - a

#

let me edit it rq

sharp meteor
#

calm ty guys

thorny flameBOT
#

@topaz onyx

sharp meteor
#

.close

topaz sinewBOT
#
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pure talon
#

how should I approach this integral?

topaz sinewBOT
pure talon
#

this integral looks so evil

#

it looks difficult to u-sub

stiff knoll
#

it doesn’t look awful

#

have you tried $u = 1/x$ ?

thorny flameBOT
#

Médicis

pure talon
#

OHH

#

i tried e^1/x

stiff knoll
#

you’re welcome haha

pure talon
#

howd u figure out it u should be 1/x?

stiff knoll
#

My first thought was that e^1/x is hard to integrate so you better simplify it to e^u

My second thought was that by u-substitution the 1/x^2 would get cancelled out, so that would give you the neat answer

pure talon
#

i actually didnt think of that

#

I got an answer yippee

#

now i just need to check it

stiff knoll
#

well played!

pure talon
stiff knoll
#

isn’t the answer A ?

#

show me your calculations pls

pure talon
#

OH MY DAYS I FORGOT A NEGATIVE

stiff knoll
pure talon
#

i forgot a negative and that derailed me to get C

pure talon
#

new answer and fixed calculations

stiff knoll
#

well played

pure talon
#

YIPPEE

topaz sinewBOT
#

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proven eagle
#

hi, can some explain to me how the denominator breaks down? i'm not getting it

mint crescent
thorny flameBOT
#

Civil Service Pigeon

mint crescent
#

$=(a^2)^{3/2} (1+\tan^2 \theta)^{3/2}$

thorny flameBOT
#

Civil Service Pigeon

mint crescent
#

$=a^{2(3/2)} (1+\tan^2 \theta)^{3/2}$

thorny flameBOT
#

Civil Service Pigeon

mint crescent
#

$=a^3 (1+\tan^2 \theta)^{3/2}$

thorny flameBOT
#

Civil Service Pigeon

mint crescent
thorny flameBOT
#

Civil Service Pigeon

proven eagle
#

THANK YOU SO MUCH!!! ❤️ 🙏🏻

mint crescent
#

!done

topaz sinewBOT
#

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proven eagle
#

.close

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royal sky
#

what is the level curve related to exact equations in ODE?

royal sky
#

and is it like really importatnt to understand further concepts in ODE

#

this is pretty much all the context i have

normal storm
#

did u just click on all of the roles

#

💔

topaz sinewBOT
#

@royal sky Has your question been resolved?

pseudo sonnet
# royal sky what is the level curve related to exact equations in ODE?

given a constant c, a level curve (corresponding to c) of a two variable function f is the set of inputs (x, y) for which f(x, y) = c.

an ODE of the form M(x, y) + N(x, y)y' = 0 is exact if you can find a potential function f satisfying f_x = M(x, y) and f_y = N(x, y). in that case, you can write the ODE as f_x + f_y y' = 0. considering y as a function of x, this equation is equivalent to the equation d/dx f(x, y(x)) = 0 by the (multivariate) chain rule, so f(x, y(x)) = c for some constant c. but this is precisely a level curve of f!! so in other words, the solutions to an exact ODE are given implicitly as the level curves of the potential function MenheraSalute1

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north heath
#

can someone explain the Rtu thing

topaz sinewBOT
quartz summit
#

have you been helped

north heath
topaz sinewBOT
# north heath can someone explain the Rtu thing

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

chilly walrus
#

R_tu is the region over which you are integrating

#

it's just its name

quartz summit
#

okay so what is the question?

#

sorry just wondering if it was answered

topaz sinewBOT
#

@north heath Has your question been resolved?

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north heath
#

.reopen

topaz sinewBOT
#

north heath
#

thats the question

topaz sinewBOT
#

@north heath Has your question been resolved?

north heath
#

anyone?

#

<@&286206848099549185>

neat jasper
#

draw a line from.u=0 to u=t

#

and from.t=0 to t=M

chilly walrus
#

t goes from 0 to M
u goes from 0 to t

north heath
#

this is a double integral so its calculating volume

neat jasper
#

that shape is a triangle

north heath
#

the shape is an area

chilly walrus
#

the area is the domain

#

on which you evaluate the function

north heath
#

and where is the function

neat jasper
#

single integral calculating area integrates over a line segment

chilly walrus
#

it's not shown on the graph

north heath
#

so the function is on the 3d space that is inside the triangle cordinates for any z

neat jasper
north heath
chilly walrus
#

exactly

north heath
#

how would it look like

chilly walrus
#

it would be 3d

#

idk what f and g are

#

can you send them?

neat jasper
#

this looks like its from proofwiki

north heath
#

just use any functions you want

#

on a line segment it would be something like this on the line ab

chilly walrus
#

yes exactly

north heath
#

if we have a function on that triangle how would this space we calculate look like

chilly walrus
#

3d volume

#

let me plot it

north heath
north heath
neat jasper
#

is this the Laplace transform of a convolution?

neat jasper
#

did i write the page? lol i might have, i used to write for the wiki

#

but this is probably prime mover

#

yeah he did it for this

#

anyway, not relevant

chilly walrus
#

this is the volume

north heath
#

can you show me the function itself

#

without the volume

chilly walrus
#

the full thing?

#

it looks a bit funny because of z-fighting errors but here you go

topaz sinewBOT
#

@north heath Has your question been resolved?

topaz sinewBOT
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void rune
#

simple math question for a distribution is -F(x-l) *(-x+l) = F(x-l)**2

timber jetty
#

$-F(x-l)\times (-x + l) = F(x-l)^2$?

thorny flameBOT
#

This is sad 😢

timber jetty
#

@void rune Is this your question?

void rune
#

yes

old crypt
#

Yes, assuming F is a value or a variable, and not a function

void rune
#

yes F is a variable thx !

topaz sinewBOT
#

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devout veldt
#

can someone explain to me why this diverges

devout veldt
#

.solved

topaz sinewBOT
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neon iron
#

hi

topaz sinewBOT
neon iron
#

i need help understanding this question

timber jetty
#

hi

neon iron
#

yoo

#

whats good

#

whats the difference between a quadric surface/ cylinder and a surface of revolution

#

<@&286206848099549185>

tacit lintel
topaz sinewBOT
#

@neon iron Has your question been resolved?

patent owl
# neon iron whats the difference between a quadric surface/ cylinder and a surface of revolu...

technically, cylinder = solid cylinder, which you cannot really create by revolving a function. (bonus question: why?)
a hollow cylinder without "lids", however, are also surfaces of revolution. some shapes and surfaces, such as an ellipsoid, are also surfaces of revolution.
however, every possible surface cannot be created by revolving a function. (e.g. a hyperbolic paraboloid or "pringle" shape, or an elliptic paraboloid)

#

so some quadric surfaces are solids of revolution, but not all. and of course, all solids of revolution are not inherently quadric

neon iron
patent owl
#

yes. there's a generating "radius function," as you aptly put it, and that's revolved to create the surface

#

though this generally doesn't give you an implicit equation for the surface

neon iron
patent owl
#

in practice, not really. the main "application" of a solid of revolution is finding its volume by integrating something based on the "radius function"

#

(in this case, you have an 'inner' and 'outer' radius to give the shape some thickness)

#

in theory, you could possibly find a parametrization of the shape, especially in spherical/cylindrical coordinates oriented along the axis of rotation. but whether that leads to a clean implicit surface, i'm not sure (i doubt it)

neon iron
#

a trace of a surface is where the surface intersects the planes right

#

what do they mean by the coordinates of the focus

patent owl
#

i.e. focus = vertex

neon iron
patent owl
#

well, those are the planes you are intersecting with

patent owl
thorny flameBOT
#

χασιβ ♥

patent owl
#

think like a system of equations, but instead of a point of intersection, you're now getting an equation of intersection

neon iron
#

and when finding intersects i would set 2 variables = 0

patent owl
#

yeah this will be different to traces

#

but you can eliminate one variable here (you should expect to get 2, since you need 2 to define a parabola)

#

any guesses as to which one?

neon iron
#

when the generating curve lies on the axes

#

is that not?

#

well

#

i think when y = 5 the shape is up right

#

shifted up?

#

thats what i assume

#

wso the center is y =7

#

i mean 5

#

<@&286206848099549185>

patent owl
patent owl
#

you can only assume that if the shape is constant between 0 and 5, in this case it's a different parabola

neon iron
#

i thought the trace was this

#

@patent owl this is what i mean, is this what the question is asking for ?

#

i dont understand tbh

#

i know they want this intersection

patent owl
patent owl
#

but if you want to, just set y=5 instead of y=0

patent owl
#

so there's a few ways to think about this

topaz sinewBOT
#

@neon iron Has your question been resolved?

topaz sinewBOT
#
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oblique sky
#

Exo 5 eq2

topaz sinewBOT
oblique sky
#

Im confused

#

I assume my path is so far correct

#

But idk how to continue it

neon iron
oblique sky
#

I forgot to write it 🤦‍♂️

#

What about now

#

x²≥-2

neon iron
neon iron
#

"and...."

#

"solve the following equatiuons and.."

oblique sky
#

inequations

#

equations and inequations in R

neon iron
#

ah

oblique sky
neon iron
oblique sky
#

its analysis

#

i think so yeah

#

So with x≥1/2

neon iron
#

then x is greater than or equal to 1/2

neon iron
#

do you know why

oblique sky
#

Square root thing

neon iron
#

right

#

unless youre dealing with complex numbers which i doubt

#

this is real analysis right

#

not that im experienced in the field but i doubt complex numbers would be involved in a RA class right

oblique sky
#

The module has both real and complex numbers

#

But in this chapter it's only real numbers

#

So S=[1/2,+inf[?

#

@neon iron just to make sure

neon iron
oblique sky
#

its ok

neon iron
#

[ ] means include the endpoints

() means dont include the endpoints

#

can you ever include infinity?

#

whats infinity

neon iron
oblique sky
neon iron
#

no im just asking

#

like to make sure you understand the bounds

oblique sky
#

in class the prof usually uses [] to include/not include endpoints

neon iron
#

or she

#

im not saying you cant use ] ever

oblique sky
#

[ on +inf

neon iron
#

huh...

oblique sky
#

different education systems maybe?

#

does the symboles change overtime

#

do highschool students and uni students use the same symboles to include and not include end points?

neon iron
#

cause think about it

#

whats infinity

#

when you "include" infinity by writing ]

#

what are you including?

#

you arent reaching any number it just keeps increasing

#

its a notation convinience thing

#

and an intuitive thing too now that i think about it

oblique sky
#

ok so theoratically lets say we're not including a real number like 12

neon iron
#

so i dont think its universally correct to use ] in inf

oblique sky
#

is the interval gonna be [1/2,12[

#

or is it [1/2,12)

neon iron
neon iron
#

youre including 1/2 and values all up until 5 but not 5

#

so you can include 4.9999

#

for example

oblique sky
#

so its gonna be [1/2, 5)?

neon iron
#

i just forgot to mention the example

neon iron
oblique sky
#

ok

neon iron
oblique sky
#

i think the symboles differ in each country

#

i'll go ask the prof tomorrow

#

maybe he was wrong

#

maybe he wasnt

#

but i understand your point in here

#

@neon iron after some research

#

it appears that we were both right

oblique sky
#

yours is the standard one

neon iron
neon iron
oblique sky
#

Ikr

#

I never knew that till now

#

So anyway

#

How do we close this channel

topaz sinewBOT
#

@oblique sky Has your question been resolved?

#
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orchid hatch
topaz sinewBOT
orchid hatch
#

it asks for a+c

#

isn't that just 62+78

#

so 140

exotic dome
#

Yaah

orchid hatch
#

ok

#

and for b it asks for what is b

#

so is b just 40

#

180-140?

orchid hatch
#

ok

orchid hatch
#

todays hw is ez

#

i helped teacher

exotic dome
orchid hatch
#

if l and m are parallel what is x

orchid hatch
exotic dome
orchid hatch
#

yea

#

is it 62?

#

wait

torpid shard
#

i think you got the idea right but the math wrong anyways

orchid hatch
#

42

#

use the triangle?

torpid shard
#

yes

orchid hatch
#

this

#

In the diagram below, AD is perpendicular to BC and DE is parallel to CA. If ∠BCA = 68◦,
find ∠ADE, in degrees

#

similar triangles?

torpid shard
#

oh yeah, nevermind

orchid hatch
#

aww

#

find DAC?

torpid shard
#

didnt understand the idea for a sec

orchid hatch
#

ok

torpid shard
#

Yeah, basically, BE is colinear to AB (in fact, its a part of it) and DE and AC are similar.

orchid hatch
#

ye

torpid shard
#

So they fit the criteria for being similar triangles

orchid hatch
#

is EBD right or smth

#

no mb

torpid shard
#

Nope, consider the 90 degree you got near it

orchid hatch
#

EBD and ABC are similar

#

OH

#

its 180-90-68

torpid shard
#

yep

orchid hatch
#

so 22

#

In triangle ABC, AB = AC. Let D be a point on side AC such that AD = BD. If ∠DBC = 66◦,
then find ∠BAC, in degrees.

#

isocelese triangle so

#

hmm how do i do this

exotic dome
orchid hatch
#

wha

exotic dome
#

Do sum of angles in ABC

orchid hatch
#

ok

#

is ADB 180-2x

#

ok

#

2x+66+y=180

exotic dome
#

What is y

orchid hatch
#

hmm

exotic dome
#

ABC is isocèles

orchid hatch
#

x+66

#

so 3x+132=180

#

x=16

#

so its just 16?

exotic dome
#

Yes I didn’t check the math. But should be yeah

orchid hatch
#

ok

exotic dome
#

Test it

orchid hatch
#

let me get online

#

ok

#

yea

#

ima ask him

#

In the diagram, BC is parallel to DE. If BD = 2, BC = 12, and DE = 21, then find AD.

#

set up an equation

#

AB = x

#

(2+x)/21=x/12

#

x=24/9?

#

or 8/3

#

so in total 14/3

#

i think

exotic dome
#

The equation is correct

#

The rest I don’t know

#

I never do the math

orchid hatch
#

correct

orchid hatch
#

im 1/2 done

#

In triangle ABC, ∠ABC = 90◦. Points P and Q are on side AB so that AP = PQ = QB, and
CP = 7 and CQ = 5. Find BC

#

hmm

#

AC is 9 or smth?

#

BC is 3???

rough furnace
orchid hatch
#

i got QB as root(8)

orchid hatch
rough furnace
#

Yeah that's right

orchid hatch
#

ok

rough furnace
orchid hatch
#

do BC is

orchid hatch
#

BC is sqrt(17)

rough furnace
#

Seems true

orchid hatch
#

ok

#

then

#

AC is

#

root(89)

rough furnace
#

Yeah

orchid hatch
#

ok

#

In triangle ABC, M is the midpoint of AB, N is the midpoint of AC, and G is the
intersection of BN and CM. The area of triangle GMN is 6. Find the area of triangle GBC

#

the two triangles are similar

rough furnace
#

Yeah

orchid hatch
#

ok

#

what ratio though

#

i think 12

#

stupid guess

rough furnace
#

I don't think it's 12

orchid hatch
#

ye

#

its 9 or 12

rough furnace
#

NM should be half BC

#

That's obvious

orchid hatch
#

oh

exotic dome
#

24

orchid hatch
#

dam

rough furnace
#

Mannnn

exotic dome
#

Not 12

rough furnace
#

nosolsssssss

orchid hatch
#

.nosols

rough furnace
orchid hatch
#

!nosols

topaz sinewBOT
#

As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

exotic dome
#

Ok ok

orchid hatch
#

i might be randomly picked to go over this problem

exotic dome
#

No sols ! Think !

#

You got half the answer already

orchid hatch
#

?

#

its .2 and then another .2

#

cuz base ratio is 1/2

rough furnace
#

Think about the height of each triangle

orchid hatch
#

and height ratio is 1/2

rough furnace
#

You already have the base of each

#

Yeahhhh

orchid hatch
#

yea

#

so 6.2.2

#

so 24 ye

#

10 is just area of ABC

rough furnace
exotic dome
#

GMN and GBC are similar

orchid hatch
exotic dome
#

With a ratio of 1/2

rough furnace
#

Ohhh

orchid hatch
#

and are wise that is .4

exotic dome
#

Meaning the ratio between their areas is 1/4

orchid hatch
#

oh shoot

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i realized there is a second page ☠️☠️⚰️⚰️😭😭💀💀✌️✌️

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quesitons look ez

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like that asks for degree ABC

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Let A, B, C, and D be four consecutive vertices of a regular nonagon. Two of the sides are
extended to meet at P, as shown below. Find the degree measure of ∠ABC

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isn't that just 140

rough furnace
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Huhhhhh

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ABC???

orchid hatch
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yea

rough furnace
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So what's P even used for

orchid hatch
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next question

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Using the same diagram as in Problem 14, find the degree measure of ∠APD.

exotic dome
exotic dome
orchid hatch
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lol

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how do you find APD

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its a pentagon

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so angles add to 540

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BAD and CAP are 40 each

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Bad boy likes to cap

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long DCB and long CBA are both 220

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so APD is 20

exotic dome
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What ! 😂

orchid hatch
exotic dome
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Me or the 20 ?

orchid hatch
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no

exotic dome
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I was thinking of a more complicated way so if you found 20
Easily

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Stick with it

orchid hatch
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oh

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so it is 20

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i need to find ABC

exotic dome
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The area ?

orchid hatch
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yea

exotic dome
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Remind me of what we know

orchid hatch
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this diff

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its not 20

orchid hatch
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for that

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GBC is 24

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and GMN is 6

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fot this DPA is 20

rough furnace
exotic dome
orchid hatch
orchid hatch
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pls

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is it correct?

exotic dome
orchid hatch
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wah

exotic dome
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I never do the math let’s try it another way

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Look at triangle OND

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NOD is 90

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OND is 140/2 =70

orchid hatch
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no

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its a pentagon
so angles add to 540
BAD and CAP are 40 each
Bad boy likes to cap
long DCB and long CBA are both 220
so APD is 20

exotic dome
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That leaves ODN = 180 -70 -90 =20

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So I agree

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Meow

orchid hatch
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ok

exotic dome
orchid hatch
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we have to find ABC

exotic dome
orchid hatch
exotic dome
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Ok can we call MNG = X

orchid hatch
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ok

exotic dome
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X is the area of MNG ok ?

orchid hatch
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ye so its 6

exotic dome
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Do you agree that MNB = 2 MBC ?

orchid hatch
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mhmm

exotic dome
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Same height , basis x2

orchid hatch
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yea

exotic dome
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So 6 + MGB = 2(24+ MGB)

orchid hatch
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mhmm

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wiat

exotic dome
exotic dome
orchid hatch
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ok

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-42 = MGB/

exotic dome
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So find MGB

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Huh ?

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Wait

orchid hatch
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6+MGB = 2(24+MGB)

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6+x=48+2x

exotic dome
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Wait

exotic dome
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It’s MBC = 2 MNB

orchid hatch
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oh lol

exotic dome
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Now split each of them to find MGB

orchid hatch
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i was confused for a sec

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2(6+MGB) = 24+MGB

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12+2MGB = 24 + MBG

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MBG =12

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wiat

exotic dome
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Ok now do you agree that MNB = MNC

orchid hatch
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ye

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mnc?

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oh ye

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nvm

exotic dome
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So that means that : MGB = NGC

orchid hatch
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yea

exotic dome
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Cause they share MGN