#help-27

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stone silo
#

Hi I have the set ${ ax+b | a,b \in R \ \text{with} \ a \neq 0 }$ that defines all polynomials with degree 1 and the relation ~ where $ax + b \sim cx + d$ if $\frac{a}{c} > 0$. I need to check whether its reflexive, symmetric, antisymmetric and transitive. Is my solution correct? \
(1) Its reflexive because given $ax + b$, since $\frac{a}{a} = 1 > 0$, $ax + b \sim ax + b$. \
(2) Its symmetric because if we have two polynomials $ax + b$ and $cx + d$, if $ax + b \sim cx + d$, there are two cases for $a$ and $c$, the first one being $a, c > 0 => \frac{c}{a} > 0$ and the second one being $a, c < 0 => \frac{c}{a} > 0$ which implies $cx + d \sim ax + b$ \
(3) Not antisymmetric because for example $5x + 8 \sim 6x + 4$ (as $\frac{5}{6} > 0$) and $6x + 4 \sim 5x + 8$ (as $\frac{6}{5} > 0$) even though $5x + 8 \neq 6x + 4$ which means it cant be asymmetric \
(4) It is transitive because if $ax + b \sim cx + d$ and $cx + d \sim ex + f$ then $a$ and $e$ always have the same sign meaning $\frac{a}{c} > 0$

sullen island
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use $\sim$ for ~

woven radishBOT
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aPlatypus

stone silo
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thx

sullen island
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also if you want a line jump in the latex you need to add two new lines

woven radishBOT
stone silo
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sorry

sullen island
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eh its fine we're not born latexers

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not sure what you're doing in 2), how does that show symmetry ?

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and a small typo in 4), you mean a/e right

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@stone silo

stone silo
woven radishBOT
stone silo
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and since $\frac{c}{a} > 0$ is true, $cx + d \sim ax + b$

woven radishBOT
sullen island
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yeah I guess that works too

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alright

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@stone silo Has your question been resolved?

stone silo
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so is everything fine? @sullen island

sullen island
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yes

stone silo
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alright thanks

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gusty flume
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Hi.

devout snowBOT
gusty flume
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So I need some helps on an ODE. The question is $(x-y)dy=dx$ and I can't seems to find a correct answer.

woven radishBOT
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alstom.metropolis

gusty flume
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Here's the original question.

supple knot
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did you learn how to solve first order linear differential equation

gusty flume
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Mhm.

winter radish
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rewrite it to dy/dx = first then use substitution

gusty flume
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Give me a second to get my scrap paper real quick.

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since i already wrote it down before

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found it

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i'm checking the first part before concluding the ODE, but it doesn't have anything wrong

winter radish
gusty flume
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since i already consider u=-y already at the tabular part

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hybrid leaf
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hybrid leaf
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How does 1/theta^2 + 1 become tan^-1 when integrated

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I forgot how to do edy💀

pseudo basin
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$\dv{x} \tan^{-1}(x) = \frac{1}{x^2+1}$

woven radishBOT
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ann.in.a.teacup

hybrid leaf
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Is that just something I’m supposed to memorize?

pseudo basin
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you can figure this out by differentiating both sides of x = tan(y) and doing some rearrangement shit -- but also this should be on your formula sheet anyway

hybrid leaf
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Is there no explanation behind it?

pseudo basin
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there IS an explanation

hybrid leaf
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Ohh ok ok then

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Then I won’t bother highkey don’t wanna know💀🙏

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Thanks for the help

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forest shuttle
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genuinely lost

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frozen aurora
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square both sides

forest shuttle
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why can't i square every part and get (7-4x)+(3-2x) = 1

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that ends up at 6x = 11 and it's not a valid answer

frozen aurora
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(1+2)^2 = 3^2 = 9
1^2 + 2^2 = 1 + 4 = 5

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$(a+b)^2 \neq a^2 + b^2$

woven radishBOT
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artemetra

forest shuttle
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what

iron kindle
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,tex .wrong square

woven radishBOT
iron kindle
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$(a+b)^2=a^2+2ab+b^2$

woven radishBOT
forest shuttle
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what are you guys doing

winter radish
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$(a+b)^2 \neq a^2 + b^2$

woven radishBOT
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loopyloop

forest shuttle
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why is everybody doing this

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what's going on

winter radish
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square both sides

frozen aurora
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you can't individually square it

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it will be incorrect

olive snow
forest shuttle
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you're telling me to isolate one radical and square both sides that way

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i am so tired

forest shuttle
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.close

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stone helm
#

how to calculate dna share with my cousin?

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supple knot
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sir this is a math server

lunar eagle
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LMFAO

heavy current
lunar eagle
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this needs to be a sticker

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pls

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im begging

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can i ping the mods

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or i do i get ban for thta

heavy current
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do not

lunar eagle
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😔

heavy current
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they will not add this as a sticker

lunar eagle
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too good to be missed out

heavy current
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I guess… I’ll close this then kongouderp

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stone helm
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....

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HELP ME...

iron kindle
stone helm
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it is a question

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it ends with a question mark

iron kindle
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runic pumice
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can anyone double check my work?

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runic pumice
shadow brook
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Looks correct to me.

runic pumice
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thank you!

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can someone check this aswell?

ionic coyote
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looks good!

runic pumice
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did the calculations for this one my calculator because for some reason it wasnt letting me input fractions as the answer. Hoping thats just an issue with the question lol

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prisma walrus
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what's the general formula to calculate t for any given number based on the pattern in this table

or at least how do i solve it

prisma walrus
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<@&286206848099549185>

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😭

spare crypt
prisma walrus
prisma walrus
spare crypt
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oh sure

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so exponential stuff looks like y=a*b^n

prisma walrus
spare crypt
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a is the number at n=0, and b is the multiplier change between n

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so here it's a=1 and b=2

prisma walrus
prisma walrus
spare crypt
prisma walrus
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still needle
#

Am I going insane? If f(5) outputs 3 and f(3) = 5 how is this turning out incorrect?

desert arch
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Teacher is a dumass mby

still needle
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😭 😭

desert arch
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What grade is this?

still needle
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its college pre calc im a freshman

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i just started so theyre reviewing composition of functions

desert arch
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Then it exists for sure

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Its just 5 nothing more to say

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Complete robbery

restive river
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Try 4 for the meme

still needle
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didnt work but thanks for the idea

desert arch
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Real madrid typa robbery

still needle
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i gotta email the teacher lmao

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tropic skiff
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can someone check my work? not just the numbers, but preferably any minor issue that might get points taken off

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@tropic skiff Has your question been resolved?

tropic skiff
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!helpers

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To ask for mathematics help on this server, please open your own help channel or help thread. See #❓how-to-get-help for instructions.

tropic skiff
#

<@&286206848099549185>

eternal bobcat
#

the first 3 sections look about right

eternal bobcat
tropic skiff
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Wait didnt you say youre taking this in the next unit

eternal bobcat
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yeah we did this today lmao

eternal bobcat
tropic skiff
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-# liar

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(either way id prefer to wait for another person to verify)

eternal bobcat
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makes sense lol

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midnight scroll
#

okay someone PLEASE explain how i can find the height of this triangle

acoustic leaf
#

do you know the triangle area formula?

midnight scroll
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a=1/2bh

acoustic leaf
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out of those variables, which ones do you know? which ones don't you know?

midnight scroll
#

i know b = 5.9

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acoustic leaf
#

any other variables that you know?

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vernal flame
#

Could some one please help explain method of joints please?

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@vernal flame Has your question been resolved?

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vernal flame
#

<@&286206848099549185>

acoustic leaf
#
  1. find external reaction forces
  2. draw an FBD at each joint consisting only of the external forces and the internal forces of the ties connecting to that joint
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restive river
#

You basically first find global equilibrium, so do your support reactions and such

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then, for each 'pin' just where two members meet, you want to find one where you have at least one known force, and then just solve for the other forces.

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So, in this situation, you can start with joint A and find
FAB and FAF, then move on to the second joint with this information, id personally pick joint B, but you can also pick joint F. Keep doing this for all joints.

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This smells like a Hibbler Statics problem

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bleak arrow
#

how were these relationships derived?

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dry oxide
#

is this from physics or vector calculus

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looks like differential length elements in different coordinate systems

bleak arrow
bleak arrow
dry oxide
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i can explain the cartesian/rectangular one but i’m not too sure about the other two

bleak arrow
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can we derive them through parametrization?

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isn't dl = T dt?

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= r'(t) dt

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or is that for cartesian coordinates only

dry oxide
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ye that works for cartesian coordinates since dL is just the derivative of the position vector

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but for cylindrical and spherical, the basis vector change with position so it's not as simple as just differentiating r(t) like in cartesian

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sorry but i barely have any knowledge about spherical and cylindrical

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dry oxide
bleak arrow
#

it's like this

dry oxide
#

it wasn't like this before lol

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bleak arrow
#

what do i do

devout snowBOT
bleak arrow
#

there you go

dry oxide
#

yea 👍

bleak arrow
#

do i post the question again

dry oxide
#

yea sure, i'm sure someone would help you

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acoustic leaf
#

arc length formula $s=r\theta$

woven radishBOT
devout snowBOT
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@bleak arrow Has your question been resolved?

spare crypt
#

er I guess for dL specifically it's just like chain rule, you can convert with stuff like dr = (dr/dx dx + dr/dy dy + dr/dz dz)

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junior cradle
#

The base of a solid is the region bounded by the graphs of y = root x and y = (1/8)x^2.
a. Find volume if the cross sections are semi circles on the x -axis
b. find volume if the cross sections are equilateral triangles on the x-axis

i am super confused on how to get this set up, but once it’s setup i know i can integrate it

junior cradle
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for part a how do i find the radius

tardy edge
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vertical distance between the curves

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i think

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given that it revolves around x axis right

junior cradle
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i don’t think this is revolving

tardy edge
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oh

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but

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since they're both

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functions of x

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then it's dx

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therefore yeah

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it is

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vertical distance between the curves

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would be your radius

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mb diameter*

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radius would be half of that

junior cradle
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it’s not necessarily a solid of revolution

tardy edge
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yeah

junior cradle
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ik that area = 1/2 pi r ^2

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but in my notes i just what what r =, and i have no idea how i got there

tardy edge
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i still believe the radius is half the distance between each curves

junior cradle
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so

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(rootx - x^2/8)/2

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wait i think im doing it

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nvm

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i got that completely wrong

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ok

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did algebra wrong that’s all

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.close

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north mountain
#

pls help

devout snowBOT
north mountain
#

hmwk pls, let n be positive integer

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prove that there is no solution for 2^{n+3} | 3^n +7 exists

topaz crag
north mountain
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yes dat

topaz crag
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Thanks

faint gorge
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induction?

north mountain
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no weak proofs pls

faint gorge
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what

north mountain
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do it

thin inlet
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modulo 3 implies n must be even

north mountain
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ik

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leads no where

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tried playin with 9^k + 7 = (1+8)^k + 7 = sum binom(k,i) 8^i + 7 mod 2^{2k}

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i go sleep, i wake up pls make proof & ping me, night night

faint gorge
north mountain
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no weak proofs no induction or zesty goofy ahh proofs, wont bother readin

faint gorge
#

xddd ur tripping

north mountain
#

ye

topaz crag
north mountain
#

use axiom of choice & p-adics

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that will get job done night night goofy ahhs

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.close

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heavy current
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granite anvil
#

is the first line not wrong here?

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signal ginkgo
#

what a name in a math server

granite anvil
#

im getting $[sec^2(xy)]x\dv{y}{x}$

woven radishBOT
#

gamer75431

signal ginkgo
#

first line is right

granite anvil
#

how so

signal ginkgo
#

you remember product rule?

granite anvil
#

dont we take the inside argument after taking deriv of tan

solar goblet
granite anvil
#

oh

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flip

signal ginkgo
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yea

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its chain rule, then product rule

granite anvil
#

okok

#

thank you

#

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cerulean rock
#

is anyone familiar with r studio?

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@cerulean rock Has your question been resolved?

cerulean rock
#

are u stupid

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cant u see

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that no one answered my question

#

fricking bot

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sick lantern
#

Can anyone explain to me a clear definition of a gradient vector in MVC

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steel plank
#

i know this is a question of physics but can anyone help me in this ?

steel plank
#

<@&286206848099549185>

wispy oyster
#

lenz' law

#

when the north pole comes closer to the ring

#

magnetic flux is increasing but the ring does not like that so it opposes that by generating its own magnetic flux in the opposite direction (causing an anticlockwise current)

#

try figuring out when the magnet is moving away from the ring

devout snowBOT
#

@steel plank Has your question been resolved?

steel plank
wispy oyster
#

indeed

steel plank
#

but when magnet is passing through the coil after sometime the coil will interact with south pole and clockwise current will be generated so answer should be D

#

but ans is C

#

@wispy oyster help

wispy oyster
#

ah I see, the question is only asking what happens when the magnet is brought near to the ring

#

it is not asking what happens when the magnet is pushed away from the ring

steel plank
#

the loop is attached to the wallopencry

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vernal ferry
#

We draw five slips from a hat with each slip labelled 1-100. Each time we draw a slip, we can label it "largest," "second largest," "third largest," "fourth largest," or "fifth largest." Our goal is to maximize the chance that these five numbers we pulled are in exact order as labelled. Describe a strategy that we could do and provide estimates of the probability that that strategy would be successful.

pseudo basin
#

as in, we draw these slips one at a time and we have to give each one a label before we draw the next?

pseudo basin
#

uhh

#

wait did you translate the problem or was it given to you in English

vernal ferry
#

it was given to me in english

pseudo basin
#

ok

#

well there is kind of a stupid strategy that seems to just be intuitively the best possible

#

for the first slip, assign it one of the 5 labels according to which of the intervals 1-20, 21-40, ..., 81-100 it falls into

vernal ferry
#

thats kind of what i was thinking too

#

but how would i estimate the probability this wwould be successful

#

is where i got stuck

graceful cosmos
#

A very rough estimate is just finding the probability of drawing 5 labels 1,2,3,4,5 in the right order

vernal ferry
#

that would just be 1/120 no?

graceful cosmos
#

Exactly. I imagine that's a low estimate

vernal ferry
#

yeah

#

ig thats the most simple estimate i cud give

graceful cosmos
#

I'm sure better can be done, I'll think on it

vernal ferry
#

haha yes thank u very much

graceful cosmos
#

Or no, wait, I didn't get my idea right. Instead, let's say we can draw from 1,2,3,4,5 with replacement. Given we do 5 draws, what's the probability we get one of each?

vernal ferry
#

one of each as in like in not repeating

#

?

graceful cosmos
#

No need for getting them in order, just one of each

#

Yeah, no repeats

vernal ferry
#

thats like 90 percent

#

100times99tims98times97times96/100^5right?

graceful cosmos
#

I mean only from the labels 1,2,3,4,5

vernal ferry
#

ohhh

graceful cosmos
#

That one is 120/5⁵

#

I imagine that's like drawing from the intervals 1-20, 21-40, etc

vernal ferry
#

yeah so like 3 percent

#

OH

#

i see waht u mean

graceful cosmos
#

You have to draw from one of each interval

vernal ferry
#

what u mean

#

OHHH

graceful cosmos
#

I'm ignoring cases like drawing 19 and 20, so this is still a rough estimate

#

But yeah, I think it's a bit higher than 3%

vernal ferry
#

that makes a lot of sense

#

okok yeah but it gives a strong rough estimate

#

gotcha

#

thank u very much

graceful cosmos
#

Again I wonder if better can be done

vernal ferry
#

mhm

#

good point

#

i think

#

honestly ive thought abt this for almost an hr now so that much is good progress lol

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#

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junior whale
#

Hello, I'm trying to prove the following question:

You are given the two equations f, g : (0, π/2) -> R for which the following statements hold:
|g(x) - g(y)| <= (x - y)^2 for any x, y in (0, π/2]
g(x) = f(x) * sinx
f(π/4) = sqrt(2)

Prove that:
the equation of g(x) is constant for x in (0, π/2]

I've tried a lot of things but none of them seem to work. I need a push in the right direction, thank you for your time.

devout snowBOT
#

@junior whale Has your question been resolved?

junior whale
#

oh wait

#

!show

devout snowBOT
#

Show your work, and if possible, explain where you are stuck.

junior whale
#

ill do that rn

#

ill show something that i tried

#

i didnt arrive at a contradiction, so i couldnt prove that g(x) is in fact a constant function

#

and not a function where g(x) can be greater than or less than g(y), for some x in (0, π/2] and some y in (0, π/2]

devout snowBOT
#

@junior whale Has your question been resolved?

north mountain
#

prove that g'(x) = 0

#

for any x in (0, pi/2)

#

$|\frac{g(y)-g(x)}{y-x}| \leq |y-x|$

woven radishBOT
#

Goëtia

north mountain
#

then : $\lim_{y \rightarrow x} g'(y) = 0$

woven radishBOT
#

Goëtia

north mountain
#

u can then deduce than g'(x) = 0 , thus g(x) = c => g(x) = f(x) sin(x), plug x = pi/4 , u got what u need @junior whale

junior whale
#

thank you

#

it does indeed come out that g'(x) = 0

#

ill close this then

#

tysm~

#

how do iclose

#

!close

#

.close

devout snowBOT
#
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junior whale
#

.resolved

#

.resolve

#

why hasnt it gone back?

#

there arent many free channels left, i wouldnt wanna inconvenience anybody

final dune
#

.reopen?

junior whale
north mountain
#

not it will be free'd soon @junior whale

junior whale
#

it's resolved so...

#

oh okay

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severe prairie
devout snowBOT
severe prairie
#

how do i do this? a is part 1

#

ik i forgot the rotation above origin at angle theta for a but idc ab that

#

also ignore the bottom issa diff q

#

<@&286206848099549185>

silver crane
#

please ping after 15 min

#

rotational transformation?

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silver crane
#

and linear transformation?

#

not sure tho

devout snowBOT
#

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kindred mauve
devout snowBOT
kindred mauve
#

needs marking checking for corrections

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@kindred mauve Has your question been resolved?

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long drift
devout snowBOT
pseudo basin
hazy cradle
#

whats the ques?

pseudo basin
#

to solve this system of inequalities, i would assume

#

OP is gone tho which is sad

hazy cradle
#

OP?

pseudo basin
#

original poster

long drift
#

Could someone solve this plesse?

pseudo basin
#

!noans

devout snowBOT
#

The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.

pseudo basin
#

we won't solve this for you, but we can see what you've tried and give you pointers for how to proceed

#

if you are really completely absolutely stuck without even the smallest idea that's still ok (but tell us so)

devout snowBOT
#

@long drift Has your question been resolved?

long drift
pseudo basin
#

wow ok hold on

#

ok i can see you are on the right track (and also i have made a mistake in my own solution) but this can probably be written a little better

#

so alright our goal here is obviously to solve each one of the inequalities to eventually take the intersection of their solution sets

long drift
#

Yes!

pseudo basin
#

for inequality II, you've got it broken down into sin(x)(2cos(x) + 1) ≥ 0

#

so what i would do here actually is plot its solution set on one circle rather than breaking it down into two

#

easier to show what i mean so let me sketch a pic

long drift
#

Alright.

#

Thank you very much!

pseudo basin
#

something like this

#

this is kind of an extension of the wavy curve method to a circle

#

the way i'm using it, inside the circle means negative and outside means positive

#

& i don't care much for it being to-scale radially, but all of the crossing points are explicitly marked here in green

#

0 and pi from the sin(x), 2pi/3 and 4pi/3 from the 2cos(x) + 1

#

so then i see for inequality I you decided to break it into two cases based on when the denominator was positive vs negative

#

wait actually

#

do you understand what im suggesting for II

#

i wanna make sure we're on the same page here before i move on to I

long drift
#

Yes yes!

#

Thanks!

#

The solution given is impossibile but jm not understanfing why!

pseudo basin
#

impossible huh

#

well let's just keep going with inequality I shall we?

#

so what i would do here is more or less follow you and first rewrite it as $\frac{1 - \sin(x) - \sqrt{3} \cos(x)}{\cos(x)} > 0$

woven radishBOT
#

ann.in.a.teacup

pseudo basin
#

then also multiply both sides by $-1$ just to have a bit less minus signs to deal with, so $$\frac{\sin(x) + \sqrt{3}\cos(x) - 1}{\cos(x)} < 0$$

woven radishBOT
#

ann.in.a.teacup

pseudo basin
#

and then also do the same thing you did with the R-formula (or whatever else you wanna call it) and reduce to $$\frac{2 \sin(x + \pi/3) - 1}{\cos(x)} < 0$$

woven radishBOT
#

ann.in.a.teacup

pseudo basin
#

so far so good?

#

@long drift

long drift
#

Right!

pseudo basin
#

so when it comes to doing the circular wavy curve method, the denominator changes sign at 3pi/2 and pi/2 while the numerator changes sign at pi/2 and 11pi/6

#

which i believe you also worked out in your work

#

sin(x + pi/3) = 1/2 etc.

long drift
#

Yes!

pseudo basin
#

the upshot is that at pi/2, numerator and denominator both change sign, so the sign of the fraction does not change there

long drift
#

Okk

pseudo basin
#

so we get this kinda thing

#

i've got colored pens on me so i am using two different colors on one circle

long drift
#

Alright!

#

Thanks

pseudo basin
#

and i've also put hatch marks of the relevant color in the regions where each function is the right sign

#

if you dont have colors what you could do is draw a number line from 0 to 2pi that's like your circle unrolled into a straight line

#

and plot the intervals for each inequality that way

#

and then take their intersection

long drift
#

Yes yes i did that

pseudo basin
#

so anyway you can see there is no overlap here

#

that's why the solution set is empty

#

@hazy cradle what's with the skull react?

long drift
#

Oh right!

#

So what mistakes did i do?

#

Maybe with sin2x...

pseudo basin
#

no, II is perfectly fine as far as i can tell.

hazy cradle
pseudo basin
#

i think your biggest mistake was trying to do this all symbolically rather than using unit circle diagrams and keeping yourself in check visually

#

with rational inequalities you can sorta get away with this, but with trigonometric ones it is much much harder

long drift
#

Alright!! Thankss!! Ill check maybe better thank you very much!

#

Yes this one is tricky!

pseudo basin
#

and this system in particular imo is quite beefy

long drift
#

Yess thank yiu very much!

hazy cradle
pseudo basin
#

do you know the wavy curve method

#

like for non-trigonometric ineqs

#

this thing i'm doing here is an extension of that to trig

#

which i think is pretty elegant

hazy cradle
#

damn

pseudo basin
#

its the same idea but just wrapped around a circle

#

anyway yeah ok

hazy cradle
#

sheesh, gotta look it up

#

might be useful for my studies

pseudo basin
#

@long drift do you have anything else to ask for now? or are we good

#

you can .close the channel if you're done

long drift
#

I ve also found this

pseudo basin
#

it looks the same in terms of the overall idea but there is a lot more table-bashing and unintuitive visuals for my taste

long drift
#

Altight

#

Ill keep it open for a second just to check something

devout snowBOT
#

@long drift Has your question been resolved?

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pure mesa
#

We are given a function ft(x)=tsin(tx) and are told that two neighboring zero points have tangents which touch at an angle of 28 degrees for a certain value of t

pure mesa
#

this is what I did, but I do not think that it is correct

#

can someone tell me why I am wrong and how to fix it?

#

(my approach btw is that if the angle of them together has to be 28 degrees and they have the same slope then the angle with the x axis has to be half of that at 14 degrees)

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#

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pure mesa
#

We are given a function ft(x)=tsin(tx) and are told that two neighboring zero points have tangents which touch at an angle of 28 degrees for a certain value of t

pure mesa
#

this is what I did, but I do not think that it is correct
can someone tell me why I am wrong and how to fix it?
(my approach btw is that if the angle of them together has to be 28 degrees and they have the same slope then the angle with the x axis has to be half of that at 14 degrees)

devout snowBOT
#

@pure mesa Has your question been resolved?

supple knot
#

the angle (1/2) * alpha being 14 degrees gives you the slope. so find the equation of the tangent line and solve for the slope by finding the angle beta.

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granite anvil
#

is the inverse wrong here?

devout snowBOT
granite anvil
#

my teacher wrote y = loga(x)

supple knot
#

where exactly there's like 10 things written on that screenshot

granite anvil
#

she said "we know that the invrse of y = a^x is y =loga(x)

supple knot
#

this is correct

granite anvil
#

but then right beside that she wrote what i think is right?

#

yeah

#

shouldn't it be loga(y) = x

supple knot
#

this is the work that proves ^

granite anvil
granite anvil
#

i feellike this one is right

supple knot
#

x and y are just dummy variables

#

the inverse of y = 2x is y = (1/2)x

#

you can just think of it as convention to write the inverse function of $y=f(x)$ as $f^{(-1)}(x)$ as a function of the same variable $x$

woven radishBOT
#

riemann

granite anvil
#

im still confused kinda

#

how can they both be right when they are saying different things?

supple knot
#

uh huh

#

they're not saying different things

granite anvil
#

isn't y = loga(x) the same as a^y = x

supple knot
#

again, the inverse function is, by convention, written in terms of the same variables y = f^(-1)(x)

#

do you agree that $f(x) = 2x$ and $f^{-1}(x) = (1/2)x$ are inverses of each other?

woven radishBOT
#

riemann

granite anvil
#

y = 2x
x = 2y
y = x/2
so ye

supple knot
#

great. same logic applies to $y = a^x$ and $y = \log_a(x)$

woven radishBOT
#

riemann

granite anvil
#

x = a^y

#

loga(x) = y

supple knot
#

it's right there

granite anvil
#

yeah

#

that one makes sense

#

i understnad ur saying its js convention for the other

#

but i dont get what you mean rly cuz dont variables have to serve a prupose

#

like how can x and y be interchangeable

#

when she writes y = loga(x)

supple knot
granite anvil
#

yes

supple knot
#

"ye" sounds like yes

granite anvil
#

i do

supple knot
#

you swapped x and y there

granite anvil
#

yes

#

oh

#

oh

#

okok

supple knot
granite anvil
supple knot
#

wut

#

what

#

can you use complete sentences

granite anvil
#

how can log_a(y) = x and y = loga(x) both be inverses of y = a^x

#

i understand how log_a(y) = x is the invrese

#

but if that one is the inverse of y = a^x, then how can the other also

supple knot
#

you wrote this right?

granite anvil
#

yes

supple knot
#

x = 2y

#

is like log_a(y) = x

granite anvil
#

yeah

#

what about the other one

#

thats js writing it in logarithmic form isn't it?

supple knot
#

what

granite anvil
#

from which she js swaps the x and y

granite anvil
# supple knot it's right there

in the screenshot of log_a(y) = x, is this just the expression of y=a^x as a logarithm while the line log_a(x) = y is the inverse of y=a^x

supple knot
#

$y = a^x$ implies $\log_a(y) = \log_a(a^x) = x$

woven radishBOT
#

riemann

supple knot
#

no inverses happening ^

#

$y = \log_a(x)$ is telling you that the inverse of $y = f(x) =a^x$

#

is $y = f^{-1}(x) = \log_a(x)$

woven radishBOT
#

riemann

#

riemann

granite anvil
#

yeah ok that makes sense

#

thank you

#

.close

devout snowBOT
#
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runic loom
#

Hey I'm working on solving DEs by substitution and i've been given a bernoulli equation. I'll show the steps i've taken so far up to where i've gotten stuck

\begin{align}
\dv{y}{x}&=y(xy^4-1)\\
\dv{y}{x}&=xy^5-y\\
\dv{y}{x}+y&=xy^5\\
n&=5\\
u&=y^{1-n}=y^{1-5}=y^{-4}\\
y&=u^{-\frac{1}{4}}\\
\dv{y}{x}&=-\frac{1}{4}u^{-\frac{5}{4}}\dv{u}{x}\\
-\frac{1}{4}u^{-\frac{5}{4}}\dv{u}{x}+u^{-\frac{1}{4}}&=xu^{-\frac{5}{4}}\\
-\frac{1}{4}\dv{u}{x}+u&=x\\
-\frac{1}{4}\dv{u}{x}&=x-u\\
\dv{u}{x}&=4(u-x)\\
\end{align}
woven radishBOT
runic loom
#

steps 1-3 are manipulating it into proper form
steps 4-7 are setting up the substitution
step 8 is applying the substitution
steps 9-12 are manipulation

#

and by proper form, I mean
$$\dv{y}{x}+P(x)y=Q(x)y^n$$

woven radishBOT
runic loom
thin inlet
#

linear ode

#

your goal with bernoulli odes is typically turning it from bernoulli ode into a linear ode

thin inlet
#

then you'll have u(x), and you can replace u with y

runic loom
woven radishBOT
thin inlet
#

errr

#

my point was more solve the linear ode

#

this was the whole point of getting it down to a linear ode

#

so solve the linear ode in terms of u, i.e. get u(x)

#

then using the fact u=y^-4, you get u(x)=(y(x))^(-4)

runic loom
runic loom
thin inlet
#

its a linear ode

runic loom
#

solved it

#

.close

devout snowBOT
#
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devout snowBOT
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devout yarrow
#

quick questiion, why is integral calc chaging the 2-3x? I'm guessing its the absolute value but im not sure why

distant helm
#

you're correct

#

its the absolute value

#

|A| = |-A|

devout yarrow
distant helm
#

yea

devout yarrow
#

ok thanks

#

.close

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remote elbow
#

how to do 49

devout snowBOT
solar goblet
#

it is helpful to first do a similar problem, but in 2d instead

pseudo basin
#

well, that or you can just bash it.

winter patrol
#

did you do 48?

pseudo basin
#

48 is harder, no?

remote elbow
scarlet jacinth
#

if annyone can help me with this pls do

winter patrol
#

the question involves distance between points
so consider applying distance formula

winter patrol
devout snowBOT
#

@remote elbow Has your question been resolved?

remote elbow
#

how to apply it

#

to find the set

winter patrol
#

have you applied the distance formula before?

devout snowBOT
#

@remote elbow Has your question been resolved?

remote elbow
#

im not at home now

#

i can’t do it rn

devout snowBOT
#

@remote elbow Has your question been resolved?

devout snowBOT
#

@remote elbow Has your question been resolved?

silk phoenix
remote elbow
#

so i got midpoint

#

now how to get plane

silk phoenix
#

You just need vector of those 2 points though

#

And midpoint

devout snowBOT
#

@remote elbow Has your question been resolved?

devout snowBOT
#
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#
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broken wagon
#

I'll send my work in a second

devout snowBOT
broken wagon
#

Just ping me when possible to let me know what I did wrong, I appreciate it

low sentinel
#

🙂

broken wagon
#

Oh I did, that's not good but thanks for letting me know

low sentinel
broken wagon
low sentinel
broken wagon
#

Unfortunatly

low sentinel
#

try 54.7164

broken wagon
#

It worked

low sentinel
#

k

#

!done

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#

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broken wagon
#

.close

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radiant ore
#

for systems of equations how do you choose whether to eliminate y or x

junior flax
#

Or

wind mason
radiant ore
junior flax
#

Guass!

wind mason
#

Let's say you have a system like:
100x+y=0
-99x+y=3
You're obviously eliminating the y here.

junior flax
wind mason
# radiant ore

Yeah, both of these involve prime numbers. Just multiply out the ones that seem smaller.

wind mason
wind mason
radiant ore
#

just relised i did the second part wrong lol

crude wasp
# radiant ore

tbh i think for like school it's probably easier just to do lots of practice rather than trying to optimise eliminating x or y, i don't think it makes too much of a difference here

junior flax
#

Go the unkindly path, eliminate only in the most algebraically confusing and computation intensive ways! (For the real ones)

radiant ore
#

it doesnt

#

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crude wasp
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pallid stream
#

there are 15 points as in the picture. what's the probability of 3 randomly chosen points NOT being colinear?

pallid stream
#

now here's the thing

#

I got 1223/1365 while the correct answer is 1221/1365

#

so that means I'm off by 2, which means I can already be proud of myself lmaoooo

#

idk if I did it right (well obviously not since I'm mistaken) but I started by writing down all the ways you could choose the points that are colinear (so that I can subtract later in order to get the ones that aren't colinear)

#

and idk if there's a faster (and more importantly, correct) way of doing it

restive river
#

yeah the technique is good

#

probably you just missed some

#

possibilities

pallid stream
#

yeah

#

oh wait wait wait I got one more way

#

but that still leaves me with 1 way I don't have

#

well no

restive river
#

lol

pallid stream
#

okay so now I have 1222.5/1365

#

I need 1.5 way less

restive river
#

how do you get 0.5 in odds

pallid stream
#

well because I divided it by 2

#

in reality there are 2445

restive river
#

oh right

#

my bad

west summit
pallid stream
#

yeah I got these

#

the extra one I just found is vertical

#

actually I confused myself bc of the fractions lol I originally needed 4 more ways and now I need 3

west summit
#

you got the horizontal ones I suppose?

pallid stream
#

I can show my solution

#
  1. horizontal lowest layer
    5*4*3
  2. horizontal 4th layer
    4*3*2
  3. horizontal 3rd layer
    3*2*1
  4. diagonal with 5
    2*5*4*3
  5. diagonal with 4
    2*4*3*2
  6. diagonal with 3
    2*3*2*1
  7. slope 1/2
    2
  8. vertical
    1
#

and all the ways are 15*14*13

pallid stream
west summit
#

why are you multiplying diagonal with 3 by 4?

pallid stream
#

bc there are 4 ways you can get them

west summit
pallid stream
#

I'll draw it

west summit
#

hrizontal and verical

pallid stream
#

oh wait

#

you're right bruh

#

I also included the ones that are already in diagonal with 4 bruh

west summit
#

ohh, yeah

#

so what is the actual sum?

pallid stream
#

I'll fix it

west summit
#

do you double count the vertical?

pallid stream
#

uhhh bad news

#

now there's a lot more than it should be

west summit
#

...

pallid stream
#

1228.5/1365

#

I was closer when I started lmfao

pallid stream
west summit
#

I guessed that you divided the whole thing by 2 as to not double count right-left and left-right.

#

and you cant do that with vertical/horizontal

pallid stream
#

I'm confused

#

well when you pointed out the diagonal with 3, I just swapped the 4 at the beginning for a 2

#

and that's it

west summit
#

my bad. Thought you counted in a different way

pallid stream
#

and 2*3*2*1 is indeed 12 ways that I "lost"

west summit
pallid stream
#

2457 instead of 2445

west summit
#

do we care about order?

pallid stream
#

there are 2 ways

pallid stream
#

well if I scrap these too then there's gonna be a whole lot more I missed lmao

pallid stream
#

I'll edit the message maybe

west summit
#

yeah, I just looked back, my bad

pallid stream
#

no worries

west summit
#

but 3x2x1 cares about the ORDER in which we choose the points

#

and that's goes for all the other ones aswell. Is that what the problem stated?

pallid stream
#

it doesn't really state anything

#

just "3 randomly chosen points. what's the probability of them not being colinear"

west summit
#

It doesn't matter(I think). You just have to d the same for the calculation of all points. And you do that

pallid stream
# pallid stream

but for example if you chose 2 ones from the left diagonal "line" and 1 from the top of the right diagonal "line" then they wouldn't be part of the same line, so I'm choosing to count them separately as 2*3*2*1

#

idk if that's about order

#

well for some reason my solution is wrong and I'm now missing 12 ways

rustic jetty
#

you should get a fraction over 455, not 2730

#

because order doesnt matter

pallid stream
#

huh?

rustic jetty
#

the number of ways to choose three points out of the fifteen is 15c3

#

not 15p3

pallid stream
#

what's c and p

west summit
rustic jetty
#

ah okay sure

#

so just make sure everything is ordered then

pallid stream
#

also 455 is basically 1365 in the fraction

#

bc 1365 is like the expanded fraction

#

the correct answer is 407/455, but since I got 1223/1365, I multiplied it by 3 to figure out how wrong I was lmao

#

and 407/455 is 1221/1365

pallid stream
west summit
rustic jetty
pallid stream
#

aight

west summit
#

where does 2730 come from?

rustic jetty
#

15x14x13

#

you ordered everything except the lines with slope 1/2 and the vertical line

#

so slope 1/2 should be 2 * 3 * 2 * 1

#

and vertical should be 3 * 2 * 1

#

which gives the the given answer

west summit
#

ohh, ok

#

So, we have:

horizontal lowest layer
5x4x3
horizontal 4th layer
4x3x2
horizontal 3rd layer
3x2x1
diagonal with 5
2x5x4x3
diagonal with 4
2x4x3x2
diagonal with 3
2x3x2x1
slope 1/2
2x3x2x1
vertical
3x2x1
and all the ways are 15x14x13

#

@rustic jetty

pallid stream
#

it isn't tho

rustic jetty
#

read after

pallid stream
#

idk why I didn't count them like this even tho I did it with everything else bruh

#

thank you so much

west summit
#

.close :)

rustic jetty
#

np lol

pallid stream
#

.close

devout snowBOT
#
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west summit
#

It was fun while it lasted @pallid stream @rustic jetty

devout snowBOT
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granite anvil
devout snowBOT
granite anvil
#

what is the question asking?

#

idk what f^6(0) is referring to

#

the 6th deriv when it is equal to 0?

coral heron
#

yes

wind mason
granite anvil
#

damn

#

ok

#

thanks

#

.close

devout snowBOT
#
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devout snowBOT
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uneven talon
#

This is my explanation of why its true that the columns of an n x n matrix A are linearly independent when A is invertible. Is this a good explanation?

solar goblet
#

what's the clown emoji for

uneven talon
kind tiger
#

if you made it up then you need to define what it is

uneven talon
#

i thought pivot was a generally well-known term

stone stump
#

it is

uneven talon
#

The pivot or pivot element is the element of a matrix, or an array, which is selected first by an algorithm (e.g. Gaussian elimination, simplex algorithm, etc.), to do certain calculations. In the case of matrix algorithms, a pivot entry is usually required to be at least distinct from zero, and often distant from it; in this case finding this e...

kind tiger
#

ah nws then

#

i would also like to see some more reasoning as to why the rows being linearly independant means the columns must also be

#

can be as simple as just saying det(A) = det(A^T) tbh, but i think it needs to be in there

uneven talon
#

i never mentioned the rows being linearly independent though

stone stump
#

they said nothing about the rows being lin indep

#

and its not needed

kind tiger
#

oh wow yeah i cant really

uneven talon
#

the identity matrix pretty obviously has pivots in every column imo

kind tiger
#

really dont know how i read that so wrong ahah

uneven talon
#

its ok

stone stump
#

yes the explanation is fine

uneven talon
kind tiger
#

yeah sorry again for misreading so badly LOL

uneven talon
#

im worried that i made a jump from rref(A) invertible -> A invertible

stone stump
#

well presumably you are allowed to use that row reducing doesnt change linear (in)dependence between columns

uneven talon
#

Not that I don't trust it's true

#

More that I think its up to me to justify that

stone stump
#

the whole point of row reducing is basically that fact

uneven talon
#

Yeah and it makes sense given the idea of elementary matrices

stone stump
#

or phrase it as solving the linear system

#

same solutions <=> same dependencies between columns

uneven talon
#

Oh right

#

I can easily prove that Ax = 0 implies x = 0

#

Which would mean the columns of A are linearly independent

stone stump
#

yes

uneven talon
stone stump
#

yw

devout snowBOT
#

@uneven talon Has your question been resolved?

#
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devout snowBOT
#
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viscid wagon
#

,rotate

woven radishBOT
#

Couldn't find an attached image in the last 10 messages.

devout snowBOT
viscid wagon
#

,rotate

#

Question 2

#

,rotate

woven radishBOT
viscid wagon
#

I'll probably only need help with part 1

distant helm
#

Hint: $\frac{x^2}{9}+\frac{16}{x^2}=\left( \frac{x}{3} \right)^2+\left( \frac{4}{x} \right)^2=\left( \frac{x}{3} -\frac{4}{x}\right)^2+\frac{8}{3}$

#

gotta admit though, that one may be pretty hard to figure out

#

@viscid wagon

woven radishBOT
#

TargetVN

distant helm
#

sry, it's this instead

devout snowBOT
#

@viscid wagon Has your question been resolved?

viscid wagon
distant helm
#

you can do that, or just do the very obvious substitution u = x/3 - 4/x

#

do note that with this substitution, 1 value of u will output 2 values of x

west summit
#

nor can we gaurantee that they are double roots

distant helm
viscid wagon
#

Is it just A = 16/3

#

Wait ni

#

2*sqrt(8/3)

west summit
distant helm
#

,w 3A^2-32=0

woven radishBOT
distant helm
#

seems like it

viscid wagon
#

Huh how'd you get that quadratic

distant helm
#

u^2 + 8/3 = Au

which is just a quadratic

viscid wagon
#

Oh

distant helm
#

since 1 u gives 2 x, the quadratic must have 1 root only

viscid wagon
distant helm
#

i mean since we have found what is A, we can just find u

#

then find x

#

no need some fancy stuff here

#

also the word "minimum" is kinda deceptive lol, theres only 1 value of A satisfying the problem after all

viscid wagon
distant helm
#

that one is obvious for me but not for anyone else

#

then just kinda work from that point and the solution pops up over time

viscid wagon
#

Wait but

#

A = u + 4/3u >= 4*sqrt(2/3)

#

But the AM-GM inequality doesn't hold