#help-10

1 messages Β· Page 503 of 1

exotic oak
#

ye I'm not really sure how to go from there

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So not really

balmy mortar
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'sen' D:

raven spire
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Oh does the sen(x) mean sine of "x", considering your indeterminate form

exotic oak
#

oh

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sorry I thought that was universal

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sen = sin

raven spire
#

mhmm np

exotic oak
#

I thought the 2 ways were acceptable

balmy mortar
#

I think only in some languages it is written sen

exotic oak
#

Yes I'm Portuguese

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Comes from seno

raven spire
#

$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$

warm shaleBOT
balmy mortar
#

tg is tan?

exotic oak
#

yes

balmy mortar
#

That is new to me lol

raven spire
#

Do you want to use this question as an example?

exotic oak
#

Yes that's alright

raven spire
#

kay-

exotic oak
raven spire
#

so umm, first we start with this being a (+1)^infty form

exotic oak
#

exactly

#

that's where I got stuck

#

I tried L'Hopitale

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But not the best way here for sure

raven spire
#

since we're more familiar with other indeterminate forms, preferably 0/0 or infinity/infinity forms... or 0times infinity

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we want to convert this form into one of them

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'kay?

exotic oak
#

k

raven spire
exotic oak
#

Oh

raven spire
#

so, our first step is to use log properties

exotic oak
#

Some other guy here at discord told me with was applied with any indeterminations

raven spire
#

Remember $a^b = e^{b \ln a}$?

warm shaleBOT
exotic oak
#

a should be above no?

raven spire
#

given.. the log of "a" is defined

raven spire
exotic oak
#

so "e" and "ln" they dissapear and we would get b * a ?

raven spire
#

nope

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Do you remember the log properties?

exotic oak
#

yes

raven spire
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what does $a = \ln b$ imply?

warm shaleBOT
exotic oak
#

e^a = b?

raven spire
#

Yep

#

now, my question is, what is: \
$e^{\ln a}$?

warm shaleBOT
exotic oak
#

a

raven spire
#

Great

#

My next question is: what is- \
$e^{b \ln a}$

warm shaleBOT
raven spire
#

you might have to use exponent laws here as well

#

once you answer this, we might very well be able to start with your actual question

exotic oak
#

Ik it's supposed to be a^b

raven spire
#

Yep

exotic oak
#

Just not clearly getting how

raven spire
#

okayyy

exotic oak
#

In my head

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It should be

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b * a

raven spire
#

So, you have: $e^{b \ln a}$ right?

warm shaleBOT
exotic oak
#

y

raven spire
#

next, you use the exponent laws

#

$e^{b \ln a} = e^{b \times \ln a} = (e^{\ln a})^b$

warm shaleBOT
raven spire
#

Got it!?

exotic oak
#

let's just another example

#

like

#

wait

raven spire
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hmm

exotic oak
#

let me try to use the bot

raven spire
#

Let's take:

#

$2^{3\log_2 7}$

warm shaleBOT
exotic oak
#

$4^{6 \times \x} = (4^{\x})^6$

warm shaleBOT
#

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

raven spire
#

$4^{6 \times x} = (4^{x})^6$

warm shaleBOT
raven spire
#

Right ?

exotic oak
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yes

raven spire
#

that's what the exponent laws say

exotic oak
#

that's what I wanted

#

Oh okay

#

No doubts then

raven spire
#

hence we could write

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$e^{b \ln a} = e^{b \times \ln a} = (e^{\ln a})^b$

exotic oak
#

Got it

warm shaleBOT
raven spire
#

$= a^b$

warm shaleBOT
raven spire
#

Got it?

exotic oak
#

yes yes

raven spire
#

100% sure?

exotic oak
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yes

#

I said before I wasn't understanding

raven spire
#

Now, back to the actual question

exotic oak
#

If I hadn't got it I would tell

raven spire
#

$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$

warm shaleBOT
raven spire
#

Right?

exotic oak
#

yes

raven spire
#

We use the same trick to send the stuff inside the parenthesis to the exponent

#

okay?

exotic oak
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ok

#

don't say anything

#

let me try to work this out

raven spire
#

hmmm

exotic oak
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then you say if I got it right

raven spire
#

okie

exotic oak
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Just with this tip

#

okkkkk

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tough

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Cause it's so different

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nope

#

@raven spire

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Couldn't do it

raven spire
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oop

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So we do the same trick and get

#

$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$

warm shaleBOT
exotic oak
#

that's the same we had

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{\tan x \ln (\sin x - \cos x)}$

exotic oak
#

oh we need to change base

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alright

#

makes so much sense

warm shaleBOT
raven spire
#

Makes sense?

exotic oak
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yes

raven spire
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Yep

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now, which indeterminate form do you see?

exotic oak
#

let me see

#

ln(1)

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= 0

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oo * 0?

raven spire
#

Yep

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the exponent now has the indeterminate form: $\infty \cdot 0$

warm shaleBOT
raven spire
#

Next, my question is: which indeterminate form do you want this to become... that will make it most comfy for you

exotic oak
#

That's a tricky question

raven spire
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πŸ‘€

exotic oak
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I like 0/0 or oo/oo

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For L'Hopitale

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I guess

raven spire
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Great

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$=\lim_{x \to \frac{\pi}{2}} e^{\tan x \ln (\sin x - \cos x)}$

warm shaleBOT
raven spire
#

the ln part is 0 already, what would you do to make the exponent 0/0 form

exotic oak
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@raven spire

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I don't seem to be getting anywhere

raven spire
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$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\ln(1 - \cot x) - \ln(\sin x)}{\cot x}}$

warm shaleBOT
exotic oak
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Thought of dividing by tan x

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then multiplying again

raven spire
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make any sense?

exotic oak
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hm

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not really

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But that's my fault I think

raven spire
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nope

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so

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First

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$\tan x = \frac{1}{\cot x}$

warm shaleBOT
raven spire
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Yes???

exotic oak
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Because cot I never used it before I'm being honest with you

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But I guess it should be in my seventy

raven spire
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okay never mind cot..

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Tell me one thing

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Have you dealt with substitution method during solving limits?

exotic oak
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y -> 0

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something like that?

raven spire
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Yep

exotic oak
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yes

raven spire
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okay

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so

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Let $y = x - \pi/2$

warm shaleBOT
raven spire
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Then, $y \to 0$ right?

warm shaleBOT
exotic oak
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yes

raven spire
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great

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now, we substitute y = x - Ο€/2 in the expression

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$=\lim_{x \to \frac{\pi}{2}} e^{\tan x \ln (\sin x - \cos x)}$

warm shaleBOT
exotic oak
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but we don't have any x - pi/2 in the expression

raven spire
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Okay you know

#

You could actually just-

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break the tan into sine and cosine?

exotic oak
#

yes

raven spire
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$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \ln (\sin x - \cos x)}$

warm shaleBOT
raven spire
#

Now, it's 0/0 form because $\cos x \to 0$ and $\ln(\sin x - \cos x) \to 0$

warm shaleBOT
raven spire
#

Use your favorite L'hopital (γƒ˜ο½₯_ο½₯)γƒ˜β”³β”β”³

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makes sense!?

exotic oak
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I have one question

raven spire
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mhmm?

exotic oak
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sinx is the one multiplying ln(sinx-cosx) right?

raven spire
#

Yep

exotic oak
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cosx is muliplying 1

raven spire
#

yep

exotic oak
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so since sinx / cosx = 0

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it's a 0 / 0

raven spire
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$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$

warm shaleBOT
raven spire
#

No.. wait... what?

exotic oak
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0 * 0

raven spire
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"x" isn't going to 0

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It's going to Ο€/2

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cos x -> 0

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the denominator goes to zero

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and the ln term in the numerator goes to zero

exotic oak
#

cos(pi/2) is zero right?

raven spire
#

yeah (γƒ˜ο½₯_ο½₯)γƒ˜β”³β”β”³

exotic oak
#

so sin x * ln(sinx-cosx) / 0 * 1

raven spire
#

yep

exotic oak
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alright

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thank you

raven spire
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wait

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._. You ended that so vaguely I'm confused as heck

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lemme write it up for you βœ“

exotic oak
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Lim is not really my strong, sorry if it gets annoying to you or so

raven spire
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$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\fbox{\cos x}} \frac{\fbox{\ln (\sin x - \cos x)}}{1}}$

#

hmm lemme see how I can fix it (γƒ˜ο½₯_ο½₯)γƒ˜β”³β”β”³

warm shaleBOT
#

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

raven spire
#

Yeah

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well anyways

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@exotic oak the boxed terms make the indeterminate form 0/0

exotic oak
#

yes

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I got that!

raven spire
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Good luck !

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And ping me with your answer lol

exotic oak
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I will need too much luck

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ahaha

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Brb then

obtuse pebbleBOT
#

@exotic oak Has your question been resolved?

exotic oak
#

help @raven spire

raven spire
#

hehe

exotic oak
#

got hopefull that I was going the right way but solution is different

raven spire
#

Isn't it 1/e?

exotic oak
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it is

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I got "e"

raven spire
#

Well, looks like someone forgot how to differentiate as well πŸ‘€

exotic oak
#

no

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$

warm shaleBOT
raven spire
#

You had this?

exotic oak
#

Impossible πŸ˜‚

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yes I had

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x = 1}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$

exotic oak
#

then

warm shaleBOT
raven spire
#

You put sin x limiting value 1?

exotic oak
#

d/dx of sinx / cosx

raven spire
#

whaaaaaaaaaat

#

nooooooo you dum dum

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\fbox{\cos x}} \frac{\fbox{\ln (\sin x - \cos x)}}{1}}$

warm shaleBOT
#

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

raven spire
#

I told you only the boxed parts of the exponent are responsible for the indeterminate form

exotic oak
#

YES

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but

raven spire
#

If you were gonna apply L'hopital, your numerator function should've been the log function

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and the denominator must've been the cosine function

exotic oak
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ohhhh

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ffs

raven spire
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the sine x limiting value is 1 so forget it

exotic oak
#

So

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e^cos(x) + sin(x) / x / -sin(x) ?

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$

warm shaleBOT
exotic oak
#

d/dx of ln

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{ \frac{\ln (\sin x - \cos x)}{\cos x}}$

warm shaleBOT
exotic oak
#

yes

raven spire
#

$=\lim_{x \to \frac{\pi}{2}} e^{ \frac{\frac{\sin x + \cos x}{\sin x - \cos x}}{- \sin x}}$

warm shaleBOT
raven spire
#

$= e^{ \frac{\frac{1+0}{1-0}}{-1}}$

#

$= e^{ -1}$

warm shaleBOT
exotic oak
raven spire
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because differentiation chain rule

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consider revising

exotic oak
#

dude

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yes...

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sorry

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I'm just tired

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I need to replace

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1 / x with the expression

raven spire
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:p

exotic oak
#

on (x)

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thank you so much

#

finally it's done

raven spire
#

Have fun!

exotic oak
#

.close

obtuse pebbleBOT
#
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obtuse pebbleBOT
#
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near yoke
#

on the topic of limits

obtuse pebbleBOT
near yoke
#

can you apply l'hospitals rule to only the numerator/denominator repeatedly until you get to an answer for the numerator/denominator only

hazy marlin
near yoke
#

so if you

#

turn the denominator

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into a fraction of itself

#

and that is 0/0 or inf/inf

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you can use it

#

ah

hazy marlin
#

yea

near yoke
#

alr ty

#

.close

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#
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#
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upper widget
#

how do i check how many roots a quartic function has?

upper widget
#

what is the method to do so

sinful kraken
#

use formula

upper widget
#

which formula

#

thats

sinful kraken
upper widget
#

thats the quadratic formula

sinful kraken
#

thats what u asked

upper widget
#

how is that going to help

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I said how do I check how many roots a quartic has

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e.g. there is the discriminant for quadratics

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what is there for quartics

sinful kraken
#

nvm then

upper widget
#

.close

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#
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timid silo
obtuse pebbleBOT
sinful kraken
#

what do you need help with ?

#

@timid silo

timid silo
#

Hi

spiral maple
#

<@&268886789983436800>

timid silo
#

I don’t get how to do the puzzle

sinful kraken
#

i think youre supposed to write the answer of each equation in the puzzle then i think you will see a pattern that will allow you to find the code

timid silo
#

Oh

#

Uh

#

Let me try that for a sec

#

I don’t see it

sinful kraken
#

what are your answers

timid silo
sinful kraken
#

idk

#

your answers are correct tho

timid silo
#

Oh

#

Tanks

#

.close

obtuse pebbleBOT
#
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crystal wind
#

Part E, I am missing something.

obtuse pebbleBOT
spice rune
#

how did you get this answer?

sour lantern
#

should be a natural number

crystal wind
#

My first answer 4023 was from pluggin in 8 to the original equation. This current one was just me trying a difference/summation of the s(8) and s(11/4^1/3)

#

current answer has no real thought behind it. just plugging numbers in.

#

I wasnt sure if I had to only use numbers between (11/4^1/3, 8]

spice rune
#

have you tried s(8) - 2 * s((11/4)^(1/3)) ?

crystal wind
#

Why * 2?

#

But no, havent tried. just s(8) - s(the other)

#

i dont think that worked, unless I typed it wrong.

#

calculated

spice rune
#

Let $s(t_1, t_2)$ be the path travelled between $t1$ and $t2$, $T = \sqrt[3]{\frac{11}{4}}$

Then $s(t_1, t_2) = s(t_2) - s(t_1)$

Since the particle is moving in one direction for $t \in [0, T]$ and in the opposite for $t \in [T, 8]$, our answer should be:
[ \abs{s(T, 8) - s(0, T)} = \qty(s(8) - s(T)) - \qty(s(T) - s(0)) = s(8) - 2s(T) ]

warm shaleBOT
#

rept1d

crystal wind
#

Thank you! That makes sense, but where does the value of s(0) go in the final equality?

spice rune
#

oh, my bad

#

let's say s(t) = t^4 - 11 t

#

then the formula works

crystal wind
#

yeah, that makes sense!

#

The prior one still applies

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and ill try that

#

Thank you! The opposite movement part really helped me conceptualize, and that answer worked!

#

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meager belfry
#

Asking this question again: Show that any distribution function F can be written as $F = aF_c+(1-a)F_d,$ where $F_c$ and $F_d$ are continuous and purely discontinuous distribution functions respectively, and $0\leq a \leq 1$

warm shaleBOT
#

MeowingLoudly

meager belfry
#

A function F is purely discontinuous if it equals the sum of its jumps, i.e. if F(x) = $\Sigma_{y\leqx} (F(y)-f(y^-))$ for all x

warm shaleBOT
#

MeowingLoudly
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meager belfry
#

that's the definition given for this

last basalt
#

Idk if that helps

meager belfry
#

maybe

#

any way to prove this using just tools from probability?

#

like baby tools

last basalt
#

I'm not sure

#

I believe convexity would indicate that the entire line segment between any two outputs of Fc and Fd would be contained in the overall distribution space

obtuse pebbleBOT
#

@meager belfry Has your question been resolved?

last basalt
#

Then you could show theyre increasing, bounded between 0 and 1 etc

meager belfry
#

Sure

#

I'll give that a shot, thanks

warm shaleBOT
last basalt
#

Like this

#

You should be able to do this for all conditions of a distribution

#

As the set is said to be convex by that definition

#

If you prove the necessary conditions for any arbitrary combination of distributions it means there would have to exist some combination to be that of the distribution F

#

@meager belfry

obtuse pebbleBOT
#

@meager belfry Has your question been resolved?

obtuse pebbleBOT
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sage charm
#

.

obtuse pebbleBOT
sage charm
#

Currently working on situation 1

#

These are my equations Standard form:
Equation 1: -(2x) + y - 2z = 5
Equation 2: x + 3y - z = 9
Equation 3: 4x + 4y – 4z = 36

#

Bit stuck on how to then get my x y and z

green plank
#

Use triple system of equations

#

So subtract both equations 2 times

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Then sub

obtuse pebbleBOT
#

@sage charm Has your question been resolved?

obtuse pebbleBOT
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limpid roost
#

Is it possible to figure out if 3^9 is greater than or less than 4^7 without using a calculator?

raven spire
#

Yep

#

It's should be

silk galleon
#

it's useful to have $\log_{10} 2 = 0.3010$, $\log_{10} 3 = 0.4771$ memorized

warm shaleBOT
#

xdk1235

silk galleon
#

or tbh 4^7 = 2^14

#

and that's very doable

limpid roost
#

Ah, okay. Thank you.

#

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dark charm
#

How does Wolframalpha go from the summation to the alternate forms?

dark charm
#

More simplified:

#

I feel like I'm missing some rule about sums

obtuse pebbleBOT
#

@dark charm Has your question been resolved?

hushed moat
dark charm
#

Yeah but I don't understand writing out the terms

hushed moat
#

like list them out

#

starting at i=0

#

then list the term for i=1

#

...

#

try to find things that cancel out or smth

dark charm
#

Oh ok

#

that makes sense I'm stupid lol

#

.close

obtuse pebbleBOT
#
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dark charm
#

.reopen

obtuse pebbleBOT
#

βœ…

dark charm
#

Ok so I tried and now I'm here:

#

.close

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#
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fossil cipher
#

Hi

obtuse pebbleBOT
fossil cipher
#

Can someone help with indices

#

Real quick

#

Or

#

Help urgent

#

What’s the rule behind it

balmy mortar
#

look up exponent rules

#

Wrong

#

misread

#

why u got 2 different things

fossil cipher
#

Huh?

balmy mortar
#

You have 2 different things on the papers

#

I am super confused

#

anyways this is elementary exponent rules

#

look them up

fossil cipher
#

Ok

#

Are the all valid?

#

just confirming

#

Is this true?

#

Yes/No

#

Please πŸ™

#

Hello?

#

I want to make g have no indices

silent adder
#

you'll want to square both sides

balmy mortar
#

no

fossil cipher
balmy mortar
#

$$\left(g ^\frac{1}{2}\right)^\frac{-1}{2}=g^\frac{-1}{4}$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

You apply the same exponents to both sides

#

so one of your first ones just doesnt work out cus of this

fossil cipher
#

Oh ic

#

Thanks

#

.close

obtuse pebbleBOT
#
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ruby oyster
#

is the inverse of y=f(x) x=f(y)

obtuse pebbleBOT
spice rune
#

no

long sinew
#

y = f(x) makes no sense, they serve similar purpose

ruby oyster
#

hmm

#

alright

#

wait

long sinew
#

f(x) means function

timid silo
#

@ruby oyster its x=g(y)

ruby oyster
#

yes thats why i deleted it cause ik that

long sinew
#

Ah ok

ruby oyster
#

srry i am learning about inverse functions

#

and to make an inverse function

spice rune
#

the inverse of f if f^(-1)
where f(x) = y and (f^(-1))(y) = x

ruby oyster
#

you rearange to find x

#

then you change x to y

spice rune
#

and f^(-1) is just a notation for another function (like g(y))

ruby oyster
#

ahh yes

#

why do we change all x to make y

#

like the inverse of y= 3/(x-1)

#

is x= (3+y)/y

#

but you chnage the y to x

spice rune
#

3/(x-1) = y means x = (y + 3)/y

#

and x = g(y) = (y+3)/y is the inverse function

ruby oyster
#

oh

#

but you can change y to x

spice rune
#

but since you usually use x as an argument and y as a function's value

ruby oyster
#

and say it is f-1

spice rune
#

you just rename it

#

so it is y = g(x) = (x+3)/x

ruby oyster
#

perfect

#

idky im getting so confused

#

this has cleared it up

#

thanks buddy

obtuse pebbleBOT
#

@ruby oyster Has your question been resolved?

#
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frigid oracle
#

How valid is this proof? "Suppose there exists $N_0$ such that $s_n \le t_n \forall n > N_0$. Prove that if lim$t_n$ and lim$s_n$ exists, then lim$s_n$ $\le$ lim$t_n$."
Proof:
\\
Let lim$t_n$ = t and lim$s_n$ = s. Let $\epsilon > 0$, and observe that $|t_n - t| < \epsilon$ $\forall n > N_0$, $|s_n - s| < \epsilon$ $\forall n > N_0$
\\
$s_n \le t_n$ $\Rightarrow$ $s_n - s - t \le t_n - t - s$
\\
Thus: $|s_n - s| - t \le |t_n - t| - s$ $\Rightarrow$ $\epsilon - t \le \epsilon -s$ $\Rightarrow$ $-t \le -s$
\\
$\therefore s \le t$

warm shaleBOT
balmy mortar
#

\lim f(x)

#

looks a lot better in latex.

frigid oracle
#

i will keep that in mind, thanks

balmy mortar
#

How does this follow?

frigid oracle
#

you basically add - s -t to both sides

balmy mortar
#

oh nvm

#

i was reading -s+t in head

balmy mortar
#

How does this follow from the above?

#

If s is greater than s_n or t greater than t_n

#

then ?

#

===
Something helpful for this proof might be to draw a rough diagram

#

And to mark epsilon

obtuse pebbleBOT
#

@frigid oracle Has your question been resolved?

frigid oracle
#

Good point. I kind of assume it since the textbook already went through it. Because of how absolute value is defined, where $|a| = a$ if a > 0, and $|a| = -a$ if a < 0, it follows that $-|a| \le a \le |a|$, since either $a = |a|$ or $a = -|a|$.

Thus: $-|s_n - s| \le s_n - s \le |s_n - s|$ $\Rightarrow$ $-|s_n - s| -t \le s_n - s - t \le |s_n - s| - t$
\\
Repeating the same process: $-|t_n - t| \le t_n - t \le |t_n - t|$

warm shaleBOT
frigid oracle
#

.
@balmy mortar ok wait

#

i am a bit stumped

#

realized something is a bit off halfway thru my last latex post

#

wait for me while i post this idea on how to prove $|s_n - s| - t \le |t_n - t| -s$

warm shaleBOT
frigid oracle
#

Consider case 1, where $s_n - s -t = |s_n - s| - t$. $s_n \le t_n$ implies $|s_n - s| - t \le t_n - t - s \le |t_n - t| -s$.
\\
Case 2, where I got stuck because I am not sure :(. Following the same process leads us to $s_n - s - t = -|s_n - s| - t \le t_n - t - s \le |t_n - t| - s$

warm shaleBOT
frigid oracle
#

The ambiguity comes from where $|s_n - s| - t$ would fit in Case 2

warm shaleBOT
balmy mortar
#

I would say to restart your proof

#

Because there really is no need to split cases

#

What you need to do

#

is draw a rough diagram

#

and indicate what you want to show with epsilon pictorially

frigid oracle
#

what would that look like?

#

I have never imagined real analysis using pictures

#

hmmm

frigid oracle
balmy mortar
#

Maybe all, cus there wasn't that much progress

#

I'm just saying restart in terms of ideas

#

Stuff will be reused

#

In particular, like you said

#

We will take this

#

Using this, we need to prove s <= t

#

idk if the picture will help you see what you need to do with these 2 inequalities

frigid oracle
#

not sure about the picture

#

i suppose they are converging to a set number, and one is def greater than the other

balmy mortar
#

Try to draw your own

#

and mark an epsilon, basically

#

@frigid oracle ah actually, I see an error in your inital proof

#

$$(\forall n > N_0)(\abs{s_n - s} < \varepsilon)$$
$$(\forall n > N_0)(\abs{t_n - t} < \varepsilon)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

You make these claims.

#

They are not necessarily true --- think carefully why.

#

This does not follow from the defn of limit.

frigid oracle
#

what is the difference between this and the defn of a limit?

#

where N is used, instead of N_0

balmy mortar
#

recall the defn of limit

#

Limit of sequence
$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN){a_n:n\geq N}\subseteq(L-\varepsilon, L+\varepsilon)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

Or

frigid oracle
#

ah, N is a set of numbers in \bN, and N_0 is a one particular number?

balmy mortar
#

$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN)(\forall n\in\bN) (n \ge N\implies \abs{L - a_n} < \varepsilon)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

No, you misunderstand

balmy mortar
frigid oracle
#

yep

balmy mortar
#

Personally, I think this one is easier to visualize

#

The (L - e, L + e) represents an interval

#

In either case, you should realise the N_0 in the original question does not correspond to N

frigid oracle
#

how come?

balmy mortar
#

Let me write.

#

$$(\forall\varepsilon\in\bR^+)(\exists N_1\in\bN)(\forall n\in\bN) (n \ge N_1\implies \abs{s - s_n} < \varepsilon)$$
$$(\forall\varepsilon\in\bR^+)(\exists N_2\in\bN)(\forall n\in\bN) (n \ge N_2\implies \abs{t - t_n} < \varepsilon)$$

#

You should realise that the N's for different sequences are not necessarily the same

#

And moreover, then N0 in the original question has nothing to do with them

#

In fact --- the epsilons don't have to be the same either

#

But in this particular case, you can choose them to be the same if u like

frigid oracle
#

I see

warm shaleBOT
#

Shuri2060

balmy mortar
#

oops corrected

#

But what you CAN do

#

is construct a new N

#

that is helpful to you

frigid oracle
#

I just looked at the answer for this exercise

#

🀦

balmy mortar
#

The N's are differently located,not necessarily the same

frigid oracle
#

πŸ‘

balmy mortar
#

(N1 and N2 depend on epsilon)

#

So you the answer says you should take max(N0, N1, N2)

#

yes?

#

Then you can compare the inequalities

frigid oracle
#

you wouldnt mind if i shared u what my textbook says, right?

balmy mortar
frigid oracle
#

its 9.9c, btw

#

sorry for all of this

balmy mortar
#

πŸ€”

#

Your textbook doesn't even use epsilon-N to show

#

and uses some result instead

#

I mean it's honestly not hard to use epsilon-N

frigid oracle
#

Yeah, but atleast he proves the results in a more pedagogical way

balmy mortar
#

$$(\forall n\geq N_0) s_n \leq t_n$$
$$(\forall\varepsilon\in\bR^+)(\exists N_1\in\bN)(\forall n\ge N_1)(\abs{s - s_n} < \varepsilon)$$
$$(\forall\varepsilon\in\bR^+)(\exists N_2\in\bN)(\forall n\ge N_2) (\abs{t - t_n} < \varepsilon)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

You have these 3 things

#

You can combine them into one statement by setting a new N = max(N0, N1, N2)

#

$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN)(\forall n\ge\bN)$$
$$(\abs{s - s_n} < \varepsilon \land \abs{t - t_n} < \varepsilon \land s_n \leq t_n)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

You work with just the inside

#

And you can use the triangle inequality

frigid oracle
#

what does the wedge mean?

balmy mortar
#

$$\abs{s - s_n} < \varepsilon$$
$$\abs{t - t_n} < \varepsilon$$
$$s_n \leq t_n$$

#

logical and

warm shaleBOT
#

Shuri2060

balmy mortar
#

So we have these 3 statements combined

#

$$s-t \leq t_n - s_n - t+s$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

This idea

#

$$s-t \leq (t_n - t) - (s_n - s)$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

$$(t_n - t) - (s_n - s) \leq \abs {(t_n - t) - (s_n - s)}$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

I believe it's this? which would lead to the result

#

πŸ€”

frigid oracle
#

thanks @balmy mortar

#

I truly appreciate helping me out

balmy mortar
#

no ive lost how to do it, but you should be able to show via this ^

#

πŸ‘Œ

frigid oracle
#

.close

obtuse pebbleBOT
#
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obtuse pebbleBOT
#
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spring quest
#

How do you solve this question?

obtuse pebbleBOT
spring quest
#

Trigonometric stuff aren't really my thing

forest sinew
spring quest
#

I don't understand?

#

So you're saying the opposite will be the largest angle?

#

never mind this question

#

do you mind explaining what SOHCAHTOA this is?

#

is it sin or csc? <@&286206848099549185>

#

if i'm wrong please correct me.

ruby finch
#

first, draw the figure

long sinew
#

^^^^

spring quest
#

drew the figure gents

ruby finch
#

great

long sinew
#

Complementary angles

ruby finch
long sinew
#

Or that

ruby finch
long sinew
#

Both work

#

πŸ™‚

spring quest
#

this is csc right?

#

if i'm correct

ruby finch
spring quest
#

oh

long sinew
#

^^^^

#

Tangent

ruby finch
#

there's nothing to do with hypotenuse here

spring quest
#

thanks man :)

#

.close

obtuse pebbleBOT
#
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ruby finch
obtuse pebbleBOT
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strong vale
obtuse pebbleBOT
strong vale
#

What "otherwise" approach could be taken to express the quartic as a product of quadratic factors

true rain
#

You would do something like

#

$(ax^2+bx+c)(dx^2+ex+f)$

warm shaleBOT
#

KurtDee

true rain
#

But it's going to be uhhh pretty hard

strong vale
#

yh

long sinew
#

Sheesh thats a nightmare

true rain
#

So I mean like

#

if you know you have whole numbers

#

that makes it a lot easier

#

for example, a,d is pretty simple

strong vale
#

yh it would be easier

#

but no whole numbers

#

this question

true rain
#

and c,f would also be trivial

#

I'm not sure how unique this equation is

#

I dont think it is

#

I would start with those two assumptions

#

a,d is a pretty easy one to address

#

you can just factor by a,d

#

so you would get

#

$ad(x^2+\frac ba x+\frac ca )(x^2+\frac ed x+\frac fd)$

warm shaleBOT
#

KurtDee

true rain
#

which is effectively the same thing as just removing it

#

because a*d = 1

obtuse pebbleBOT
#

@strong vale Has your question been resolved?

#
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harsh phoenix
obtuse pebbleBOT
harsh phoenix
#

I need some help whit this

obtuse pebbleBOT
#

@harsh phoenix Has your question been resolved?

tardy epoch
#

You'll more likely get help if you translate it to English

obtuse pebbleBOT
#

@harsh phoenix Has your question been resolved?

obtuse pebbleBOT
#
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karmic scarab
#

help pls

obtuse pebbleBOT
#

@karmic scarab Has your question been resolved?

karmic scarab
#

<@&286206848099549185>

#

I really dont know how to solve this

sage geode
#

A product is 0 whenever one of its term is 0, which is the case here

#

Can you see why?

karmic scarab
#

how did you get 0

#

i dont see why

#

can you show it to me visually

sage geode
#

I gave you a hint that one of the terms in this product is 0

#

(Try expressing nth term using n and then looking for its zeros)

karmic scarab
#

what is nth term

long sinew
#

n is a value

#

variable

#

to be exact

sage geode
#

For example here the first term would be considered to be (1 - 9/2)

#

The 2nd term then is (1 - 9/3)

#

And so on

karmic scarab
#

yeah

#

i understand tht

sage geode
#

Clearly the nth term in this case is (1 - 9/n)

karmic scarab
#

ok

sage geode
#

Now, what happens when n = 9?

karmic scarab
#

that the one tht is changing

#

then it is 1

#

then the value is 0

#

1-9/9 = 0

sage geode
#

9th term is 0, yes

#

Meaning the entire product is thus 0 too

long sinew
#

geometric series problem?

sage geode
#

0*anything = 0

long sinew
#

fun

karmic scarab
#

thx so much'

#

tht was fun

sage geode
#

This doesn't seem to be a geometric series tho

karmic scarab
#

thx

sage geode
#

Np

karmic scarab
#

.close

obtuse pebbleBOT
#
Channel closed

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obtuse pebbleBOT
#
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timid silo
#

Hello

obtuse pebbleBOT
timid silo
#

Here, I do not understand third step:

#

You use the result from (1) and put it into (2)

#

@timid silo

#

Okay. Thank you πŸ™‚

#

.close

obtuse pebbleBOT
#
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wraith gazelle
#

I'm trying to work on 8

obtuse pebbleBOT
slate zephyr
wraith gazelle
#

We haven't learned homomorphism yet

#

Oops

slate zephyr
#

How do you define isomorphic then?

balmy mortar
#

Do you get the Q?

#

The idea behind it

wraith gazelle
#

A slight idea about it but I'm not too sure

balmy mortar
#

I usually find it helpful to use small examples

#

Say C_3 and C_5

#

Then what does the direct product look like

#

Just to get you thinking in the right direction of what the question is asking

#

I think the hard bit is seeing what the group <a> x <b> looks like if you're unfamiliar with direct products

#

@wraith gazelle Sorry that was a bit badly written by me πŸ˜‚

wraith gazelle
#

πŸ‘€

#

C_5 and C_3 as in the cyclic groups?

balmy mortar
#

yh well...

#

Basically yes

#

My example is

#

m = 15

#

a has order 3
b has order 5

#

so <a> is the same as C_3

#

<b> is the same as C_5

#

if that makes sense? same structure/isomorphic

wraith gazelle
#

I'm a bit confused about cyclic groups

#

I have a slight idea but not well explained

balmy mortar
#

Alright let me see

#

${e, a, a^2}$

warm shaleBOT
#

Shuri2060

balmy mortar
#

This is what C_3 looks like

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in general

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The structure will always be the same

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$C_n = {e, a, a^2, \cdots, a^{n-1}}$

warm shaleBOT
#

Shuri2060

balmy mortar
#

You get this part?

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a is just any 'object', it doesn't really matter...

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The group operation tells you how to handle multiplication between elements (making it work like 'normal multiplication')

wraith gazelle
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Oh I see

balmy mortar
#

What's different is a group might not be abelian

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But all cyclic groups are abelian

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Since you've just got powers of the same element

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So <a> represents the cyclic group generated by a

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if a has order m (from the question) and b has order n

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$$\langle a\rangle={e, a, a^2, \cdots, a^{m-1}}$$
$$\langle b\rangle={e, b, b^2, \cdots, b^{n-1}}$$

wraith gazelle
#

If a has an order m, does it also mean a^m=e?

balmy mortar
#

right.

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You can see that must be the case in these 2 groups.

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Note the group operation is 'borrowed' from G

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If we're going by the question

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We have the same operation, but just different domain

wraith gazelle
#

I see

warm shaleBOT
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Shuri2060

balmy mortar
#

looks better

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Alright, so now you want to think what the direct product of those 2 look like

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You are familiar with the definition of direct product?

wraith gazelle
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Not really

balmy mortar
#

you can think of it as like cartesian product

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$\bR^2 = {(a, b) : a, b \in\bR}$

warm shaleBOT
#

Shuri2060

balmy mortar
#

Similar idea, but for groups

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$$A\times B = {(a, b):a\in A, b\in B}$$

warm shaleBOT
#

Shuri2060

wraith gazelle
#

But in this case, we're doing this with order m and n?

balmy mortar
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yh... but first of all you need to be familiar with how the group operation works

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it turns out exactly how you expect in some ways

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$(a, b)(c, d) = (ac, bd)$

warm shaleBOT
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Shuri2060

balmy mortar
#

Note there are 3 different group operations going on here (but all 3 are referred to as 'multiplication)

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$(a, b)\left(_{A\cross B}\right)(c, d) = (a\left({A}\right)c, b\left(*{B}\right)d)$

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hmm that's ugly πŸ˜‚

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If that makes sense?

warm shaleBOT
#

Shuri2060

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Shuri2060

balmy mortar
#

These are 3 different binary operations in general.

wraith gazelle
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I'm a bit confused, which are from which?

balmy mortar
#

Or I could use different symbols if that makes it clearer

wraith gazelle
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Yeah

balmy mortar
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$_1:A\to A$ \
$
_2:B\to B$ \
$*_3:A\times B\to A \times B$

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Just treat them as any symbols

warm shaleBOT
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Shuri2060

balmy mortar
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$(a, b)_3(c, d) = (a_1c, b*_2d)$

warm shaleBOT
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Shuri2060

balmy mortar
#

This is an important thing to note

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So $a *_1 c$ makes sense because a and c come from A

warm shaleBOT
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Shuri2060

wraith gazelle
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And these are the operations of the three groups?

balmy mortar
#

Yes

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Because of how we defined A x B

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a, c come from A

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b, d come from B

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And by closure, ac is in A

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bd is in B

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so (ac, bd) is still in A x B

wraith gazelle
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Ah yes

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I understand

balmy mortar
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So I'm going to use a small example

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$$C_2\times C_3 = {(a, b):a\in C_2, b\in C_3}$$

warm shaleBOT
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Shuri2060

balmy mortar
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$${(e, e), (a, e), (e, b), (a, b), (e, b^2), (a, b^2)}$$

warm shaleBOT
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Shuri2060

balmy mortar
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Can you see how this is the entire group?

wraith gazelle
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How come there's no a^2?

balmy mortar
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C2

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is just

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{e, a}

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All good?

wraith gazelle
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Ah yes

balmy mortar
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So let's stick with this example

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So in the original question let's say m = 6

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So I now have <a> x < b>

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a = 2, b = 3

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and they are relatively prime.

balmy mortar
# balmy mortar

You now need to show this group must be isomorphic to the original group

wraith gazelle
#

I'm still confused how you get the whole thing

balmy mortar
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ok

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You understand I got this from the original definition, yes or no?

wraith gazelle
#

Well I understand {e,a} in C2 and {e,a,b} in C3?

balmy mortar
#

$$C_2 = {e, a}$$
$$C_3 = {e, b, b^2}$$

wraith gazelle
#

Or is it e b, and b2

warm shaleBOT
#

Shuri2060

wraith gazelle
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Oh

balmy mortar
#

C_n is the cyclic group of order n

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There is only 1 generator

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for cyclic groups

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You are familiar with that right?

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A finite group of size n is cyclic if one element has order n. If that is true, then all the elements must be some power of that element

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Then everything must be generated by it.

wraith gazelle
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Oh okay

balmy mortar
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So now this comes from me just writing out all the possible elements

wraith gazelle
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Mhm

balmy mortar
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What is (a, b)^2

wraith gazelle
balmy mortar
#

You can go step by step

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So first

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(a, b)^2 = (a, b)(a, b)

wraith gazelle
#

(a+a,b+b)?

balmy mortar
#

That all depends on the group operation

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but we usually prefer to write like multiplication

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$(a, b)^2 = (a, b)(a, b) = (a^2, b^2)$

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So like this.

warm shaleBOT
#

Shuri2060

balmy mortar
#

For the general case it will be written like this (the multiplication sign is omitted, but they are different)

wraith gazelle
#

Oh okay

balmy mortar
#

But then, this must correspond to one of these

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which?

wraith gazelle
#

(e,b^2)

balmy mortar
#

right

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because a^2 = e

wraith gazelle
#

Mhn

balmy mortar
#

For clarity, sometimes it might be written like this

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$${(e_A, e_B), (a, e_B), (e_A, b), (a, b), (e_A, b^2), (a, b^2)}$$

warm shaleBOT
#

Shuri2060

balmy mortar
#

Because e_A and e_B are not necessarily the same

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They are just the identity elements from A and B

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This is used when it is clear from context or doesn't matter.

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So which of these is the identity element of A x B ?

wraith gazelle
#

(e,e)?

balmy mortar
#

yep

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I think you get how this group works

wraith gazelle
#

I do now

balmy mortar
#

So the question...

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You need to show this thing is isomorphic to G

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Do you remember how an isomorphism works, roughly?

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Just the main concept

wraith gazelle
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Show it's bijective and morphic

balmy mortar
#

yah but the main concept is

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If we have 2 groups

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X and Y

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and they are isomorphic

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I can 'relabel' the things in X with some things in Y

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And the group will still behave exactly the same

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Just different labels (and group operation)

wraith gazelle
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f(xy)=f(x)f(y)

balmy mortar
#

Yes, that is homomorphism. And then you also need bijection

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So this isn't an easy question, there are several steps to it

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You could focus on group G first.

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It tells you $\gcd(m, n) = 1$

warm shaleBOT
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Shuri2060

balmy mortar
#

a has order m
b has order n

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Hmm

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Thinking πŸ˜‚

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Do you have any idea what this could tell you about G?

wraith gazelle
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I'm no sure

balmy mortar
#

So we have G is abelian also, forgot to mention

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But think about the element $ab$

warm shaleBOT
#

Shuri2060

wraith gazelle
#

If this helps, these are the problems that the question hints about

balmy mortar
#

Right exactly

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$(ab)^2 = (ab)(ab) = a^2b^2$

warm shaleBOT
#

Shuri2060

balmy mortar
#

First of all, the group is abelian

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So when we take powers of ab

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We can rearrange like this