#help-36

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jagged root
#

yueaa

spare summit
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but the range depends on whether the poly is of odd or even degree

spare summit
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if the poly is an odd degree poly, then the range is all real y

jagged root
spare summit
#

if the poly is an even degree poly, then the range is all y greater than or equal to the min point, or less than or equal to the max point

jagged root
#

oh

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i understand that

spare summit
#

that's the definition of degree anyway

jagged root
#

i see

spare summit
#

so x^3 + x + 1 is an odd-degree poly, for example

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while x^4 + x^2 + 3 is an even-degree poly

jagged root
#

oHH

spare summit
#

anything else you'd like to ask?

jagged root
#

uh

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I think i get it

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ty for the help

spare summit
#

nps. do close the channel when you're done with .close

jagged root
#

.close

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#
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grand flare
final saddleBOT
grand flare
#

how do i do word problems like this

deep condor
#

is $\gamma$ the radius of the sphere?

soft zealotBOT
#

حسیب ♥

grand flare
#

its r

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but ye its changing at rate of 2cm/s

deep condor
#

oh that is an r, ok

grand flare
#

hm

deep condor
#

so, we know that the radius is increasing at a rate of 2 cm/s, and we want to find the rate of change in the volume

grand flare
#

when r=7

deep condor
#

let's say the radius is $r$ and the volume is $V$, what is the rate of change of $r$? and the rate of change of $V$?

soft zealotBOT
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حسیب ♥

grand flare
#

dr/dt=2

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dv/dt=(dv/dr)*dr/dt

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?

deep condor
#

this works, yes

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now the thing we have to find is $\dv{V}{r}$, so let's find a formula with $V$ and $r$ in it, then differentiate $\dd r$

soft zealotBOT
#

حسیب ♥

grand flare
#

V=4/3 pi r^3?

deep condor
#

now differentiate both sides with respect to r

grand flare
deep condor
grand flare
#

?

deep condor
#

technically you haven't subbed $r=7$cm in yet, so you have
$$\dv{V}{r} = 4\pi r^2 \dv{r}{t}$$ for any $r$

soft zealotBOT
#

حسیب ♥

grand flare
#

now we js substitue r=7?

deep condor
#

yep

grand flare
grand flare
grand flare
deep condor
#

so why not sub in all at once?

deep condor
grand flare
deep condor
# grand flare so dv/dt=8X22/7*7X7

$\pi$ is not exactly equal to $\frac{22}{7}$, so you can either write
$$\dv{V}{t} \doteq 8 \cdot \frac{22}{7} \cdot 7^2$$
or simply
$$\dv{V}{t} = 8\pi(7^2) = 392\pi$$

soft zealotBOT
#

حسیب ♥

grand flare
#

thats why i thought to use it

deep condor
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interesting way of thinking about it, because yeah teachers do like to make things cancel

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but pi isn't 22/7

grand flare
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ohk

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ill keep that in mind

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thanks

deep condor
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you should write the "exact answer" (which is 392 pi) and then you can use 22/7 if you don't have a calculator on a test, for example

deep condor
#

so here are the general steps:

  1. write out the chain rule [ dv/dt = (dv/dr)(dr/dt) ]
  2. write the formula relating your variables
  3. differentiate to find the unknown derivative (dv/dr in our case)
  4. sub into the chain rule
  5. sub the specific time (r=7)
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do those steps make sense with what we did?

grand flare
grand flare
deep condor
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ok, sounds like a plan :)

grand flare
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is it 1/3x^2

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or 1/3*x^(-2/3)

deep condor
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if you're ever confused, sub y=x^3

grand flare
deep condor
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then $\dv{x}{x^3} = \dv{(y^\frac{1}{3})}{y} = \dv{y} y^{\frac 13}$

soft zealotBOT
#

حسیب ♥

deep condor
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beat me to it :D

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then differentiate and sub back in

grand flare
deep condor
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ah sorry, means that you did it faster than me

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like beating someone in a race

grand flare
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ahh ok

grand flare
#

in this qs my solution is
dv/dt = 27
d a^3/dt=(d a^3/da) * (da/dt)
27=3a^2 * da/dt
now a is given as a=4 because v=64
27=3*4^2 da/dt
da/dt=9/16

now we need to find dA/dt where A=area=6a^2
d 6a^2/dt
=6* da^2/da *da/dt
=12a * 9/16
putting a=4 we get dA/dt=27

final saddleBOT
#

@grand flare Has your question been resolved?

grand flare
#

?

final saddleBOT
#

@grand flare Has your question been resolved?

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plush haven
final saddleBOT
plush haven
#

Can anybody explain how this works

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I don't understand why they decided to do U sub

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I did it normally and got it right

vital crag
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u subs of the form u = ax + b are pretty trivial

plush haven
#

.close

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ripe crater
#

if im reading this right, i have to prove that

limn->infintity can = ca?

ripe crater
loud sundial
#

wdym by "cases"

ripe crater
#

so, my book says we have to consider 2 cases:

  1. c = 0
  2. c is not 0
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but, like, do i have have to consider both of em?

loud sundial
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um

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yes?

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because |c|>0 doesn't hold for c=0

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am I missing smt

ripe crater
#

makes sense

loud sundial
final saddleBOT
#

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ripe crater
#

|ca_n - ca| < epsilon
|c| |a_n - a| < epsilon
a_n - a < epsilon/c
a_n < epsilon/c + a

is this right?

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and then do it again, but at step 2 replace a_n with epsilon/c + a

cobalt sonnet
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yo

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someone helpppp

loud sundial
loud sundial
final saddleBOT
loud sundial
#

why did you drop the absolute value

ripe crater
loud sundial
#

what

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$$|c| |a_n-a|<\varepsilon \implies |a_n-a|<\frac{\varepsilon}{c}$$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
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the original limit definition has absolute values anyway

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so it's not like you need to have no absolute values in the end

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I should also say that you shouldn't start with $|ca_n-ca|<\varepsilon$ since that's assuming what you're trying to prove

soft zealotBOT
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Civil Service Pigeon

loud sundial
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but when you write it in reverse, it's fine

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I thought it was obvious at first, but perhaps it deserves a quick remark

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idk

ripe crater
loud sundial
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with the given condition?

ripe crater
#

the way i do is:
Let E > 0
then that step

ripe crater
# loud sundial with the given condition?

yeah with the given condition, or just in general

my way of doing this is:

Let E > 0
| f(x) - L| < E

then whatever e i end up getting
Let delta/N (dependong on the question) and then resolvoing it, but replacing it

loud sundial
#

You're given $\lim \limits_{n \to \infty} a_n=a$ to start with that. You want to \textit{end} at $\lim \limits_{n \to \infty} ca_n=ca$.

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

the overall methodology and rules of how to write proofs doesn't change just because what you're writing the proof about changes

ripe crater
#

im lost on what ur trying to say

loud sundial
# ripe crater im lost on what ur trying to say

You want to prove that
$$\lim_{n \to \infty} a_n=a \implies \lim_{n \to \infty} ca_n=ca.$$
When you prove $A \implies B$, it's common to start with $A$ and do stuff to end up at $B$. (Granted this isn't the only way to do this - contrapositive and other methods exist for example.) What you \textit{should not do} is start at $B$ and end up at $A$ - that would prove $B \implies A$ rather than $A \implies B$. (You may recognise this as proving the \textit{converse} of $A \implies B$ instead.) A common example of why this is an issue is because you can do stuff like
$$1=2 \implies 1 \cdot 0=2 \cdot 0=0=0$$
which allows you to end up with a true statement even if you started with a false one (\textit{vacuous truth}).

soft zealotBOT
#

Civil Service Pigeon

steady locust
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🙂

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that is what the question asks

ripe crater
ripe crater
steady locust
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you did it the other way around

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which is wrong

warm python
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Lemme try , you assume $\lim_{n \to \infty} a_n =a$ is true. From this you wish to show $\lim_{n \to \infty} ca_n = ca$

soft zealotBOT
#

c2b7_97705

ripe crater
#

how do i bring in C if i start from a_n = a?

steady locust
#

you are just multiplying both sides of the inequality by a positive number

ripe crater
#

oh

final saddleBOT
#

@ripe crater Has your question been resolved?

final saddleBOT
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halcyon roost
#

DiffEQ,
In the most recent homework two of the problems seemingly don’t appear in my notes really at all. I write everything that I said and done, so I have no idea how to solve these questions. My friends in the class had no idea either
I’ve attached my notes to this message as well

halcyon roost
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Just a way to get started would probably be ideal, especially using concepts from my notes, but any help is greatly appreciated

vital crag
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You want someone to read your notes to help you get started?

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That's the whole point of taking notes

halcyon roost
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I mean, Ive read my notes, Im not sure what part applies to these questions

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I wrote them too ig lmao

trail mango
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good handwriting

halcyon roost
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haha thanks

vital crag
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What part of the instructions in the question is confusing you

halcyon roost
#

yeah so, neither couchys theorem, superposition principle, or the wronskian really apply to verifying two parameter families of functions of nonhomogenous DEs

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Superposition deals with homogenous

vital crag
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Well do you know what the question is asking

lilac bison
halcyon roost
#

Im gonna be honest, not entirely?

vital crag
#

Yea do that first before reading your notes

halcyon roost
halcyon roost
vital crag
#

It's just telling you to plug the solution given into the DE and show that it's true

halcyon roost
#

what does two parameter mean in this context?

vital crag
#

$c_1$ and $c_2$ are called parameters

soft zealotBOT
#

riemann

halcyon roost
#

ah ok that makes more sense

lilac bison
halcyon roost
#

Yep

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trying that now

lilac bison
#

Yuh

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Getting started with differential equations?

halcyon roost
#

I guess yeah, we finished first order DEs now were onto higher order DEs

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Just plugging it in worked btw

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Thanks @vital crag @lilac bison

lilac bison
halcyon roost
vital crag
halcyon roost
#

aight thanks guys

#

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fleet briar
final saddleBOT
fleet briar
#

I am not able to understand which arc makes what angle

#

Shouldn't be angle POR = 200°?

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But I know it's wrong

strange sparrow
#

why do you think POR = 200?

heavy stump
fleet briar
#

Angle subtended by it

strange sparrow
#

hint: construct a cyclic quadliteratal involving PQR and another arbitrary point on the circumference

fleet briar
fleet briar
#

It's so confusing when reflex angles come

strange sparrow
#

Okay, say you have picked a point S on the circumference, say on the lower half of the circle (for easier visualisation)

#

what is PSR?

delicate sorrel
fleet briar
strange sparrow
#

right, can you find POR then?

fleet briar
fleet briar
strange sparrow
#

What was your previous reasoning

fleet briar
#

Seeing that other angle 100

strange sparrow
#

it's an incorrect application of the theorem

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it's just not the right shape

fleet briar
#

If not pls explain

heavy stump
strange sparrow
strange sparrow
#

sorry, just arc

fleet briar
strange sparrow
#

it is subtended by the "outside" arc

fleet briar
strange sparrow
#

they are subtended by different arcs

#

if you apply the theorem with the lime arc then it tells you reflex POR = 200 so POR = 160

#

which is another way to arrive at the same conclusion

final saddleBOT
#

@fleet briar Has your question been resolved?

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primal lava
#

Could you solve this problem? They said wrong

A. 4/7

B. 5/7

final saddleBOT
leaden moon
primal lava
#

So I need to make equal

leaden moon
soft zealotBOT
#

1 divided by 0 equals Infinity

primal lava
#

I got it

#

So my answer is wrong

leaden moon
#

And the remaing part has 3 parts shaded out of 6 equal parts

#

Note that these 6 parts represent $\frac{3}{4}$

soft zealotBOT
#

1 divided by 0 equals Infinity

primal lava
#

Thank you

#

.close

leaden moon
#

Try again

primal lava
#

.close

leaden moon
#

Don't edit 😭

primal lava
#

Sorry

#

.close

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tough pike
#

I don’t really get how I’m meant to do this question,
If Z=1+I Is a zero of the polynomial z^3 +az^2 +bz +10 -6i
Needing to find, a and b, where a and b are real

lilac bison
#

z = 1 + i?

strange sparrow
#

plug z = 1 + i into the polynomial, you will get 0

lilac bison
#

if thats the case, since its a zero of the polynomial, plugging that in, will result the equation to become zero

#

from there you have some equating to do

strange sparrow
#

from this you can equate the real and imaginary parts to form a set of equations

tough pike
#

.close

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steady wraith
#

just want to double check if im right or not because i got a slightly different answer but also it seems like the people who made the mark scheme are engineers and wrote g = 10

steady wraith
#

might as well just say e^2 = pi^2 = g = 10 by that point 💀

#

oh wait

#

it literally says

#

to use g = 10 which again feels stupid because this is maths not engineering

#

mb

#

.solved

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slow crypt
#

Hello, could someone help me to get started on this?

vital crag
lilac bison
#

oop

vital crag
#

if so then use

#

,tex .sohcahtoa

soft zealotBOT
#

riemann

lilac bison
slow crypt
#

Will the hyp be the square root of 3?

abstract bramble
#

no

slow crypt
#

Ah I'm getting my triangles confused

abstract bramble
#

what triangles

#

use pythagoreans

slow crypt
#

I thought it was one of the special ones from first glance

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It's the square root of 5

vital crag
#

the hypotenuse is sqrt(5) yes

slow crypt
#

Ah I got it

#

Lol panicked a little bit my b

#

thank you

#

.close

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hardy jackal
#

im so lost, would i not be able to do question 5 like 4?

hardy jackal
#

where am i going wrong

abstract bramble
#

uh why are you using -3 and -1

barren hound
#

i dont understand what's happening in the blue and white but the red purple and yellow is correct

abstract bramble
#

do it like question 4

hardy jackal
#

thats how my teacher showed us

hardy jackal
abstract bramble
#

2?

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i mean

#

-2

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youre trying to find the limit at -2

hardy jackal
#

but doesnt it have to be less than -2 for the first one

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my teacher did it like this

barren hound
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we care about the behaviour as it approaches -2

#

so think like -2.000000000000000000000001

hardy jackal
barren hound
#

good question

abstract bramble
#

no idea clueless

barren hound
#

thats what i woudl have done

#

plotting it at -1 is like vaguely helpful for drawing its behaviour

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but you know how to draw a line lol

hardy jackal
#

thats true

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i dont want her to dock marks for doing it another way since shes super strict about that

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idk what to do

barren hound
#

ok well uh... go ahead and plot those points but theyll not tell you anything useful about its behaviour at -2

hardy jackal
barren hound
#

what do you mean by "those points dont even work"?

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the graph should go through them

hardy jackal
#

wait ur right i mixed them up

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i switched the linear line with the quadratic

hardy jackal
#

for thise one

#

wouldnt i add arrow heads at the ends (where the blue dots are )

heavy stump
hardy jackal
final saddleBOT
#

@hardy jackal Has your question been resolved?

hardy jackal
#

can someone check these over:

gritty drift
#

First is good

#

Second is good. Small note, for continuity it is not sufficient for the right and left side limits to match. Additionally the function value at that point must also equal the limit.

#

If the left & right side limits match -> limit exists.

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If limit exists AND f(a) is equal to the limit at a -> continuity

hardy jackal
gritty drift
#

yes

hardy jackal
gritty drift
#

yes

hardy jackal
#

.close

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paper thorn
#

How do I solve this? Might be a dumbass question but it's late and can't figure it out

paper thorn
#

Do I substitute

muted prairie
#

What does the lightning bolt mean?

#

is that a 5

paper thorn
#

4

#

√x-2 + ³√4-x = 2

vital crag
#

are you supposed to find just 1 solution or all of them?

#

you could guess a solution by using 1 + 1 = 2

zinc maple
#

thats a crude guess

#

it would assume √(x-2) = ³√(4-x)

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#

@paper thorn Has your question been resolved?

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trail shale
#

What did I do wrong?

final saddleBOT
final tangle
#

you didn't mark the angle of elevation correctly

#

angles of elevation (and depression) are angles made with the horizontal

trail shale
#

What do you mean

final tangle
trail shale
#

Oh ok

#

Is this always true

final tangle
#

yes, its how these terms are defined

trail shale
#

Ok

#

But I have one question

#

My teacher told me to use alternate interior angles to “move” the angle of depression so it is in the triangle but that would make it the same angle as the angle of elevation so how does that work

loud phoenix
#

Because you will usually be given either the height or length

final tangle
#

alternate angles, parallel lines

loud phoenix
#

By moving it inside you can use your trig

final tangle
#

the above angles of depression and elevation are congruent by that property
(since the horizontals are parallel to each other)

trail shale
final saddleBOT
#

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left trail
final saddleBOT
left trail
#

For number 21 can someone tell me if I am missing something. I feel that what I found for c is not right but I can't find any errors

#

Also for the green right triangle we have phi for one of the angles and then one of the smaller right triangles has alpha as an angle. In this setup alpha can never be greater than phi right?

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#

@left trail Has your question been resolved?

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left trail
#

.open

#

.reopen

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@left trail Has your question been resolved?

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chrome ermine
#

57

final saddleBOT
steady locust
#

what does the question say to do

olive lantern
chrome ermine
#

d/dx

#

derivitave

#

sorry

olive lantern
#

arcsin(x) has a direct result

chrome ermine
#

for that one

#

i got

olive lantern
#

for the next one use the multiplication rule

chrome ermine
#

2/sqrt(1-x^2/16)

chrome ermine
olive lantern
chrome ermine
#

yes

#

-1/2(-x^2(16-x^2)+sqrt(16-x^2))

olive lantern
#

it should be $-1/2(-x^2/sqrt(16-x^2)+sqrt(16-x^2))$

chrome ermine
#

what is wrong in mine

olive lantern
chrome ermine
#

its 1/2(sqrt(16-x^2)) * -2x no?

soft zealotBOT
#

Hardik

olive lantern
chrome ermine
#

oh i forgot the -1

#

on the power rule part

olive lantern
#

so it becomes $1/((16-x^2)^(1/2)) multiplied by d(16-x^2)/dx$

#

omg

#

i dont know how to use that bot sorry

chrome ermine
#

its okay

olive lantern
#

somehow u managed to square it

chrome ermine
#

okay im going to do the whole product rule again and see what i get

olive lantern
#

ill try out the bot

#

$d(ab)/d(x) for a,b are functions of x is a'(x)b(x)+b'(x)ax$

#

bruh

chrome ermine
#

x* 1/2 (16-x^2)^-1/2 * -2x + sqrt(16-x^2)

#

thats what i got

olive lantern
chrome ermine
#

okay

olive lantern
#

thats correct for the second part

chrome ermine
#

ok

#

ok and i simplify

#

and get

#

x^2/2sqrt(16-x^2) - sqrt(16-x^2)/2

olive lantern
chrome ermine
#

can i simplify more or is that it

olive lantern
#

that will cancel out the x^2

chrome ermine
#

i see it

#

okay i understand

#

okay thanks you

olive lantern
#

dont forget

#

to add arc sin

#

deiff

#

diff

chrome ermine
#

ya

#

got it

#

ty

#

.close

final saddleBOT
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ripe crater
#

so... to solve this:
subseqeucne 1: k^2
subsequence 2: k

the limit for subsequence 1 is 1
for sub2 limit is 1/n which translates to 0

now to use the epsilon-delta/n
how would i find epsilon?

trail mango
#

can you explain your subsequences a little more

ripe crater
trail mango
#

unless i misunderstand, they do not converge (which is kinda a good thing)

ripe crater
trail mango
#

subsequence 2: k
what does this mean?

#

is that a different sequence than f?

ripe crater
#

no, the 1/n

#

so if the subsequence 1 i.e 1 if n is a perfect square is k^2
then subsequence 1 i.e 1/n otherwise can be k

or am i missing something?

trail mango
#

so you mean the subsequence f(k_1), f(k_2), ... where (k_i) is the sequence of non perfect square integers i guess

#

you're not really describing the subsequences well but you have the right idea i think

ripe crater
trail mango
#

it's ok

#

so what facts about sequences and subsequences and limits are we allowed here? i'm not sure what you are requesting still

#

now to use the epsilon-delta/n
how would i find epsilon?
like what are you talking about here?

#

are we allowed standard facts about sequences like... subsequence converges to X implies ambient sequence converges to X, and a sequence has at most 1 limit point

ripe crater
#

so, basically to prove it doesnt exist we are using the contradiction,
we say
the limit exist and then prove that, when that cant be done we say it doesnt exist

so, to do that, we need some value of epsilon

trail mango
#

ok if no standard facts at all and definitions only...
we want to show there is no L for which there is an epsilon such that for all N, there is an n >= N with |f(n) - L| >= epsilon

#

or if you insist on contradiction, sure we can say an L exists

ripe crater
#

so, how do i find the epsilon which i have to use?

trail mango
#

there are many you could pick

#

1/2 should do just fine

ripe crater
#

but how, how did we come to the conclusion that 1/2 can worl

trail mango
#

well there are subsequences converging to 0 and 1. so the limit kinda needs to be one of those (if we just imagine there is a limit for now)

#

if L = 0, then there are infinitely many n's such that f(n) = 1, so we'll be able to find one such that |f(n) - L| >= 1/2

#

if L = 1, similar thing

#

we can find large n such that f(n) is near 0 and hence |f(n) - L| >= 1/2

final saddleBOT
#

@ripe crater Has your question been resolved?

ripe crater
#

ah gotcha

#

alright alright makes sense thank you

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rustic wedge
#

HALLO
so last month apparently 3b1b posted this puzzle:
consider a ladybug starting at 12 on a clock. At any momment, it travels 1 step clockwise or anti-clockwise with equal probability (of 1/2). Every time it reaches a new number, the number is coloured red. What is the probability that the last number to be coloured is 6?

rustic wedge
#

now i just came across this

#

and i have an idea

#

the issue is i am missing something because of which i am not getting the right answer

#

Consider the following setup:
Let S be a permutation of the set {1,..,12} representing the order in which the numbers are coloured

#

clearly, the first element is fixed to be 12

#

meaning 11! elements in our sample space

#

.close

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rustic wedge
#

i am so stupid

#

why did i need to write this out to make sense of it 😭

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twin pivot
#

What Is the Quasi-Fourier Transform?

final saddleBOT
#

@twin pivot Has your question been resolved?

runic needle
#

no clue

stone wagon
sturdy cypress
#

q is quick

stone wagon
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old quarry
final saddleBOT
old quarry
#

how to integrate this

#

tried converting to sec and tan

#

but was not getting anything

final saddleBOT
#

@old quarry Has your question been resolved?

wicked obsidian
# old quarry

$$1 - 5\cos^2 x = (\sin^2 x + \cos^2 x) - 5\cos^2 x = \sin^2 x - 4\cos^2 x$$

soft zealotBOT
#

akeanti

wicked obsidian
#

looks like if u simplity the numerator like this and separate both fractions u will be left with a simple derivative

runic tulip
#

Multiply and divide by sin
Then let t = cosx

runic tulip
old quarry
#

and ill have to integrate cosec^5x

#

which in itself is a kinda long process

wicked obsidian
soft zealotBOT
#

akeanti

old quarry
#

yes

wicked obsidian
#

what is inside looks simillar to the derivative of $$f(x) = \sin^{-4} x \cos^{-1} x$$

soft zealotBOT
#

akeanti

old quarry
wicked obsidian
#

oh well

wicked obsidian
old quarry
#

yea but like u just kinda got to there

wicked obsidian
#

yea xD

stark minnow
# old quarry

why not bring cos^2x to numerator as sec^2x and let tanx=t

#

does that not work ?

old quarry
#

ull have to multiply and divide by cos^5 to get that tan term

#

and cos^5 bring to the numerator n write as sec^5

#

which ull have to break as sec^2 sec^2 sec

#

the sec^2 can be written as 1+tan^2 but what will u do about the sec

stark minnow
#

yeah i got that

#

was seeing if it is solvable further

stark minnow
old quarry
#

that is not a method they just got the answer and differentiated that..

wicked obsidian
#

it looks also possible to be solved using t=cosx and then using ostrogradsky integration method to simplify both fractions

old quarry
#

what is the ostrogradsky integration method 💀

wicked obsidian
#

smt to help with all those fractions

old quarry
#

uhh thats a bit too complicated for me

candid pulsar
#

||thats the answer||

#

a reasonable approach is to IBP on $\int \frac{\sec^2(x)}{\sin^5(x)} dx - \int \frac{5}{\sin^5(x)} dx$

soft zealotBOT
final saddleBOT
#

@old quarry Has your question been resolved?

old quarry
#

ibp on which integral

#

cosec^5x ?

#

or both

candid pulsar
#

first one

#

sec^2(x)/sin^5(x)

old quarry
#

o but how will that help?

#

ohh wait

#

Ohhhhhhhhh

#

it cancels

#

thats crazy

#

thanks bro

#

.close

final saddleBOT
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cedar obsidian
final saddleBOT
cedar obsidian
#

!status

final saddleBOT
#
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
cedar obsidian
thorny canyon
#

find the intersections first

#

can be done via substitution

loud sundial
#

,w x-2y-1=0, y^2=4x

soft zealotBOT
#

Failed to get a response from Wolfram Alpha.
If the problem persists, please contact support.

loud sundial
#

the intersections are ugly though

#

@cedar obsidian

#

You're better off parameterising the parabola by $(t^2, 2t)$

soft zealotBOT
#

Civil Service Pigeon

loud sundial
#

since this allows you to ||do Vieta's on everything instead||

thorny canyon
#

oh that's smart

cedar obsidian
cedar obsidian
loud sundial
#

um

#

oh

#

um

#

where would that come from

cedar obsidian
#

its given in the solution and i thought that the solution is messy by that algebra

thorny canyon
cedar obsidian
loud sundial
#

I see a quartic, but it's not biquadratic

#

slip of the tongue?

#

but this looks mostly like what I intended

cedar obsidian
#

am i forgetting smh

thorny canyon
loud sundial
#

idk

#

the less common usage ig

thorny canyon
#

like biquadratic is sortof a blanket term

#

any eqn of deg 4

loud sundial
#

meh I'm not in the mood to debate archaic terminology rn

#

I'll leave y'all to it since my contribution is basically done

#

the rest is algebra bash as seen above

cedar obsidian
#

.close

final saddleBOT
#
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cedar obsidian
#

oh its still open

#

nice

#

.reopen

final saddleBOT
cedar obsidian
#

solution is weird

#

it directly says that both are diameters of the circle

#

it means every chord is a diameter to a circle which is not true

opal plinth
#

No, it means every pair of chords that bisect each other are diameters

final saddleBOT
#

@cedar obsidian Has your question been resolved?

cedar obsidian
#

one more problem i need help with is this ^

opal plinth
#

Have you tried anything?

tiny kraken
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cedar obsidian
#

hello

final saddleBOT
cedar obsidian
worldly spruce
worldly spruce
worldly spruce
cedar obsidian
opal plinth
worldly spruce
#

Yeah

opal plinth
worldly spruce
#

I don't like triangles, bye

#

Best of luck though!

tiny kraken
cedar obsidian
opal plinth
opal plinth
cedar obsidian
#

BC & AC

opal plinth
#

Ok and can you find the area of AHB?

#

Or just the coordinates of H

cedar obsidian
#

area found is 16/root3

#

AHB^

opal plinth
#

Ok not sure how you got that but it's correct

#

Now what do you know about centroids

cedar obsidian
opal plinth
#

Idk what the determinant formula is

cedar obsidian
#

it divides median in 2:1

opal plinth
#

Yes

#

And ABC is isosceles, so where are all these centroids G_i

cedar obsidian
#

on the median or the altitude passing from H

opal plinth
#

Exactly

#

So what is the area of AG_1B compared to that of AHB

#

And then that of AG_2B compared to that of AG_1B...

tiny kraken
opal plinth
cedar obsidian
#

its not coming in format on (sqrt3*a^2/)/4

tiny kraken
opal plinth
#

Area of AHB

tiny kraken
#

ah, I meant the area of ABC

#

yeah divide that by 3 since H is centroid yeah

opal plinth
#

Right sure

opal plinth
cedar obsidian
opal plinth
#

No

#

Same base, but how do the heights compare?

opal plinth
#

What's the total length of the median when you say the centroid divides it in 2:1?

cedar obsidian
#

3

opal plinth
#

Right, so...

cedar obsidian
#

area is 3 times

opal plinth
#

Of what

cedar obsidian
#

the area of AG_1B is 1/3 times compared to that of AHB

opal plinth
#

No

#

G_1 is inside AHB, how can AG_1B be bigger than AHB?

opal plinth
#

Yeah ok, 1/3

cedar obsidian
#

mb for that

opal plinth
#

So can you express the sum now?

cedar obsidian
#

[
\frac{16}{\sqrt{3}} + \frac{16}{3\sqrt{3}} + \frac{16}{9\sqrt{3}} + \cdots
]

soft zealotBOT
#

BlackidoZΣ

opal plinth
#

We are not including AHB

cedar obsidian
#

oh yes sigma notation is for G_I

opal plinth
#

Yes

cedar obsidian
#

[
\frac{16}{3\sqrt{3}} + \frac{16}{9\sqrt{3}} + \frac{16}{27\sqrt{3}} + \cdots + \infty
]

opal plinth
#

Can you express this using sigma notation?

soft zealotBOT
#

BlackidoZΣ

cedar obsidian
opal plinth
cedar obsidian
#

but at the end we want to find the infinite sum right a(r^n-1)/(r-1)

#

then why not directly do it

opal plinth
#

It's an infinite sum, not a sum where the last term is "infinity"

cedar obsidian
#

i am facing problem to convert it into sigma notation

#

i need to practice that again

opal plinth
#

You divide by 3 each time

#

That means you multiply by 1/3

#

What does repeated multiplication look like?

cedar obsidian
#

1/3^n

opal plinth
#

Right

#

And then the 16/sqrt(3) stays constant

cedar obsidian
#

oh got it

#

[
\frac{16}{\sqrt{3}} \sum_{n=1}^{\infty} \left(\frac{1}{3}\right)^n
]

soft zealotBOT
#

BlackidoZΣ

cedar obsidian
#

[
\sum_{n=1}^{\infty} \frac{16}{\sqrt{3}}\left(\frac{1}{3}\right)^n
]

soft zealotBOT
#

BlackidoZΣ

cedar obsidian
#

now?

opal plinth
#

Now it's a geometric series

cedar obsidian
#

infnite gp right

opal plinth
#

Yes

#

Just be careful with the starting index

cedar obsidian
#

getting 8/root3

#

option c

#

wow its correct

opal plinth
cedar obsidian
#

when that question suddenly come in exam

#

altho at home i couldn't recall that property of median bymself

final saddleBOT
#

@cedar obsidian Has your question been resolved?

final saddleBOT
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final saddleBOT
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karmic glen
#

I am tasked with finding the supremum and infimum of this set

karmic glen
#

I need hints

#

this is first analysis course homework at my uni

#

[] denotes the floor function

#

trivial inequalities on the floor dont yield anything

#

useful

lime crest
#

{n√2} is dense in [0,1] because √2 is irrational

final saddleBOT
#

@karmic glen Has your question been resolved?

karmic glen
#

what about the infimum

cerulean epoch
#

i think this was one of the first questions i asked in this server

final saddleBOT
#
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karmic glen
#

.reopen

final saddleBOT
tiny gorge
#

simulating it numerically for say n = 1 to 1 million and checking the min result is interesting

#

chances are you'll be able to recognize what the number is, and that gives you something to aim for

karmic glen
#

okay

#

ill try that

cerulean epoch
#

you can show that inf ≥ ||1/2✓2|| using the fact that ||2, 3 are not quadratic residues mod 4|| but i'm not sure how you would show this bound is tight

karmic glen
#

0.353553

#

idk what this number is its prolly related to sqrt(2)

cerulean epoch
karmic glen
#

oh

#

mb

#

sorry

cerulean epoch
scarlet sequoia
#

The usual idea is to ||take an approximation p/q ≈ sqrt(2) through pell equation, and look at a_q||

final saddleBOT
#

@karmic glen Has your question been resolved?

karmic glen
#

$m = \lfloor n \sqrt{2} \rfloor$

We have $n(n\sqrt{2} - m) = n \frac{2n^2-m^2}{n \sqrt{2} + m}.$

Since $ n\sqrt{2} > m. $ We get $2n^2 - m^2 > 0$. Because m and n are integers this means
$2n^2 - m^2 \geq 1$.
$$a_n = \frac{n(2n^2 - m^2)}{n\sqrt{2} + m} \geq \frac{n \cdot 1}{n\sqrt{2} + m} = \frac{1}{\sqrt{2} + \frac{m}{n}}$$
Since $m = \lfloor n\sqrt{2} \rfloor$, we know that $m < n\sqrt{2}$, which implies $\frac{m}{n} < \sqrt{2}$. Therefore:
$$\frac{1}{\sqrt{2} + \frac{m}{n}} > \frac{1}{\sqrt{2} + \sqrt{2}} = \frac{1}{2\sqrt{2}} = \frac{\sqrt{2}}{4}$$

soft zealotBOT
karmic glen
#

imma look into this I didnt know you could do this

#

oh and thank you also

#

.close

final saddleBOT
#
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alpine shadow
#

Help

final saddleBOT
alpine shadow
deep condor
#

,rcw

soft zealotBOT
alpine shadow
#

B isn't the ans

deep condor
#

so what have you tried?

loud sundial
alpine shadow
#

Uh so I tried like solving the line and the parabola tgt to get sm rel bw y and m or x and m and finding the triangles area but I'm getting confused in like when I make the quadratic eqn (after solving parabola and the line) what do I do after it

final saddleBOT
#

@alpine shadow Has your question been resolved?

floral stream
#

if u have a phone, you could send pictures of what uve done

#

i can help look for errors or give hints

final saddleBOT
#

@alpine shadow Has your question been resolved?

alpine shadow
#

,rcw

soft zealotBOT
trail mango
#

bad handwriting

alpine shadow
final saddleBOT
#

@alpine shadow Has your question been resolved?

naive spoke
#

as F lies on y = mx+c asw

alpine shadow
#

Nvm I got it tysm

#

.close

final saddleBOT
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heavy plaza
#

Given $g:\mathbb{Z}/39\mathbb{Z}\to\mathbb{Z}/54\mathbb{Z}$ is a ring homomorphism, find all values of $g(1)$.

soft zealotBOT
heavy plaza
#

so im trying to find all possible homomorphisms here, but i think i need help in my understanding

#

what i have so far is that since we need $g(0)=0$, $g$ must have the form $g:x\mapsto m\cdot x + 54\cdot k$ for some $m\in\mathbb{Z}$ and for any $k\in\mathbb{Z}$, so we can say $g:x\mapsto m\cdot x$

soft zealotBOT
heavy plaza
#

so like trying $m=1$, im trying to see if thats a homomorphism. we require $g(x+y)=g(x)+g(y)$. so if we let $x=y=30$, how would we define $g(x+y)=g(60)$?

soft zealotBOT
heavy plaza
#

since g is defined only on $\mathbb{Z}/39\mathbb{Z}$?

soft zealotBOT
heavy plaza
#

guess it makes sense we'd take the input mod 39, so thatd show g(60)=g(21)=21, g(60)=g(30)+g(30)=30+30=60=6 so m=1 doesnt work

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if im right so far, how would i proceed in finding all possible m?

pure sorrel
#

hello

#

im new

heavy plaza
grim nebula
#

your ring homs aren't required to send 1 to 1?

heavy plaza
#

why would they?

grim nebula
#

err

#

that's part of the definition of a unital ring homomorphism

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commonly called just a ring homomorphism

strange sparrow
#

maybe it's actually a rng homomorphism

grim nebula
#

because people often deal with unital rings only

#

anyway

#

since 1 generates Z/39Z, you only need to worry about defining g(1)

#

since for example g(2) = g(1) + g(1)

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the one requirement is that 0 = g(0) = g(39 * 1) = 39 * g(1)

heavy plaza
#

assuming g(39)=39 ?

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oh wait no gotchu

heavy plaza
grim nebula
#

well

#

think about the ring homomorphism requirements

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g(x + y) = g(x) + g(y)

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but since every element of Z/39Z is just 1 + ... + 1 a bunch of times

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then this will always hold once you decide what g(1) is and then define g(1 + ... + 1) = g(1) + ... + g(1)

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similarly for g(xy) = g(x)g(y)

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hmmm

#

i might be lying actually

#

im definitely lying

#

g(1^n) = g(1)^n

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clearly i never work with non-unital rings

heavy plaza
#

these rings aren't unital?

grim nebula
#

nah

heavy plaza
#

1?

grim nebula
#

1?

#

wdym

heavy plaza
#

is 1 not a multiplicative neutral element in both?

grim nebula
#

thats the definition of a unital ring

#

but not the definition of a unital ring homomorphism

inland kettle
#

unital homomorphism is what snow's talking abt i think

grim nebula
#

when you define an object in mathematics, you should also define their morphisms at the same time

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so when i talk about unital rings, i really also mean with homomorphisms forced to send 1 to 1

heavy plaza
#

ohh k i got u

grim nebula
#

anyway

grim nebula
#

or just like

#

g(1^2) = g(1)^2 is enough to guarantee that

heavy plaza
#

oh k i can see that

#

so you're saying any solution x=g(1) to x^2=x mod 54 would give a valid definition of a homomorphism?

grim nebula
#

yes, unless i'm lying

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well

#

wait

#

39x = 0 is the other one i said initially

heavy plaza
#

alr, so to define a valid homomorphism, it suffices to define g(1) from the fact that addition is linear. then from the fact that multiplication is linear, we have the conditions that g(1)=g(1)^n for all n, and 39*g(1)=0.

#

g(1)=0 satisfies both, g(1) satisfies the first but not the second, and there are no other solutions to the first

#

does that sound right?

grim nebula
#

did you miss something in the second part of the sentence

final saddleBOT
#

@heavy plaza Has your question been resolved?

heavy plaza
#

i guess ;-;

grim nebula
#

18^2 mod 54 is 0

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you need x^2 = x mod 54

heavy plaza
#

ok there has to be a better way of solving this

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x^2=x mod 54 => x^2 - x - 54k = 0 => x = 1/2 +- 1/2 * sqrt(1 + 54k) => 1+54k is square => im just plugging in values of k to find square numbers

grim nebula
#

uh

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39x = 0 mod 54 => 13x = 0 mod 18

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13 and 18 are coprime so x = 0 mod 18

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that gives 0, 18, 36 as candidates

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you check their squares and only 0 works

heavy plaza
#

u absolute legend

#

just tried it on a similar problem (Z/32Z -> Z/100Z) and it's correct

grim nebula
#

nice

heavy plaza
#

my only issue still is thinking to define g by its action on 1, but from there i can now see how you'd derive those conditions

#

thanks so much <333333

grim nebula
#

if you've worked with vector spaces or abelian groups, its essentially the same idea

#

when you want to define a homomorphism of these algebraic structures, it suffices to say where the generators go

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subject to the relations they satisfy

heavy plaza
#

ah i see, i'll keep that in mind when working with them then

grim nebula
#

indeed

final saddleBOT
#

@heavy plaza Has your question been resolved?

final saddleBOT
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raven hawk
final saddleBOT
raven hawk
#

i am lost here

#

i dont know how to approach

abstract bramble
#

how many are in the large circle

raven hawk
#

80

ocean marlin
#

there are 3 circles

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and two types of balls

#

@raven hawk u still there?

raven hawk
#

yes

ocean marlin
#

cool

ocean marlin
#

Can u tell me that?

raven hawk
#

footballs

ocean marlin
#

ok

#

how many types of balls are there?

raven hawk
#

2

ocean marlin
#

Good, basketballs and footballs

#

so the entire shipment contains balls

#

meaning if a ball is not a basket ball, then it has to be a?

raven hawk
#

a football

ocean marlin
#

Good

raven hawk
#

interesting

ocean marlin
#

now lets take a look at the diagram

raven hawk
#

ive never seen a venn diaram like this one

ocean marlin
#

theres a circle that includes basketballs right?

raven hawk
#

yeah, the not basketballs is fooballs

ocean marlin
#

correct

#

so how many footballs are there

raven hawk
#

60

ocean marlin
#

good

#

now there is a large section right

raven hawk
#

yes, 40 large footballs

ocean marlin
#

good

#

thats your first answer

#

now if you have a total of 60 footballs

#

and 40 are large

#

how many are small

raven hawk
#

20

ocean marlin
#

good

#

now can u find out how many large basketballs there are?

raven hawk
#

40

ocean marlin
#

Exactly

#

now the questions asks large basketballs to small footballs

#

so that would be?

raven hawk
#

2:1

ocean marlin
#

Great

#

thats the second question done

raven hawk
#

thanks

ocean marlin
#

Np man

#

if u have any other questions, u can ask them here, or if ur done just type .close

raven hawk
#

all good thanks for the help

#

.close

final saddleBOT
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final saddleBOT
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left belfry
#

hi

final saddleBOT
left belfry
#

3+3

#

please help me

#

I am very bad at math

night raft
#

why it's 6, but you shouldn't use the help channels to troll catglasses

left belfry
#

3+3x9-2x88/3a

#

my math is linear

loud sundial
#

<@&268886789983436800> troll

left belfry
#

algebra

formal trail
#

@left belfry don't abuse the help channels like this.

#

.close

final saddleBOT
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vapid torrent
#

Some people struggle in math

#

I know people in 6th grade who struggle with 2x+6=16

night raft