#help-27

1 messages · Page 369 of 1

pseudo basin
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show the EXACT sequence of buttons pressed

sour spire
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oops guys

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the calculator didnt show it anymore

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i think i pressed smth wrongly again several times

pseudo basin
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again, reproduce it

sour spire
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sorry sorry sorry

sour spire
pseudo basin
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do the same calculation again but be careful to do it with the exact same steps as the first time

sour spire
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i did

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and it gives me 2.3

pseudo basin
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2.3 is correct

sour spire
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yess

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thankyouu smm

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very sorry for my carelessness

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.close

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opal mantle
#

How do you get BD? Is there some sort of theory I'm missing out on here? I'm in 12th grade & this is a bit embarrasing that I'm stuck on something like this lol. Shouldn't have slacked off in 9th grade...

I went & solved for BC using a^2 + b^2 = c^2, but I can't seem to figure out how to get BD. The explanation says some angle similarity theory but I have no idea what that is & would appreciate some more detailed explananation!

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#

@opal mantle Has your question been resolved?

winter patrol
#

have you drawn a pic/sketch

opal mantle
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Yea just on paper

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fervent helm
devout snowBOT
fervent helm
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how to solve this ?

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do I need to substitute values of n and just try random hit and trials?

light basin
fervent helm
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i found few values like $a_2=1 , a_3=4 , a_4=11 , a_5=26$

woven radishBOT
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Prathmesh

thick schooner
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u can rewrite the recurrence to note something about the nature of the sequence

fervent helm
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wdym by recurrence?

ebon coyote
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This sort of thing, where new terms are defined by old terms, is called a recurrence

fervent helm
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ohh

gloomy aurora
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It can be solved. Have you been taught how to solve it?

gloomy aurora
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Have you searched up any online resources? Khan academy can be quite useful.

faint hearth
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if possible, you dont want to do that here, since the solutions might be complicated exponentials

fervent helm
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there maybe some pattern

fervent helm
thick schooner
woven radishBOT
fervent helm
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yea i did that

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then?

thick schooner
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so you want to learn something about a_n - 2a_{n - 1}

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rewrite that to accomodate for that

fervent helm
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$a_{n+2} -2a_{n+1} - 1 = a_{n+1} - 2a_n$

woven radishBOT
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Prathmesh

thick schooner
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so you can imagine defining a sequence like t_n = a_{n + 1} - 2a_{n}

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to then have t_{n + 1} - 1 = t_n

thick schooner
fervent helm
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i don't understand

thick schooner
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which part?

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$\underbrace{a_{n+2} -2a_{n+1}}{t{n +1}} - 1 = \underbrace{a_{n+1} - 2a_n}_{t_n}$

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by definition^

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for convenience sake we define a new sequence t_n and we note that the difference between consecutive terms in the sequence is 1

fervent helm
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won't it be t_n+1 in the lhs

thick schooner
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yep typo

thick schooner
fervent helm
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ohh

woven radishBOT
fervent helm
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ok this makes sense

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alright then?

thick schooner
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that's it

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i mean you're tasked with finding t_{24} and t_{23}

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can you find any t_i for some i from given info

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if you can do that then you can find t_{24} or t_{23}

fervent helm
fervent helm
thick schooner
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you have a_0, a_1, and possibly some more values

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surely you can find t_0 or something

fervent helm
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yea

thick schooner
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okay so if you can find that then you can find t_{24}

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no?

fervent helm
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just a sec

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ohhh

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yea i can now

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got it.

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thank you so much

thick schooner
fervent helm
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btw how did you think all this up ?

thick schooner
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well since this looks like a jee problem or smth

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you're certainly not supposed to "solve" the recurrence

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so factorizing and hoping that there's some pattern dictating a_n - 2a_[n - 1} was the next natural step

fervent helm
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damnnnnn genius

thick schooner
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far from it 😭

fervent helm
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still that was so slay

thick schooner
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💅

fervent helm
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lol

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.close

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vivid summit
devout snowBOT
hollow ice
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well, you already know that its an arc of a circle

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and its centered at B, coz thats given

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so, all that remains is to find the angle ABC to determine how much of a circle that arc forms

vivid summit
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then bcs is 90 its a quarter?

hollow ice
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i dont understand how the other unshaded region is a quarter of a circle
And importantly, they are talking about the semicircle + shaded region,

hollow ice
vivid summit
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yh

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ok thank you

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how do i close this

hollow ice
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type .close

vivid summit
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alr thanks

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.close

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dusty fox
#

Hey, do i write 3sinx³ or 3x², the last line where i just wrote 3

fair storm
fair storm
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dusty fox
devout snowBOT
dusty fox
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I thought u put the constant at the front and then write it as is

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But the answer had -3x² -not 3x³

fair storm
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Which part are you confused about?

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You wrote: $y' = cos x^3 \cdot 2 sin x^5 \cdot cos x^5 \cdot 5x^4 - sin x^3 \cdot 3x^2 \cdot sin^2 x^5$

woven radishBOT
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Erebus

fair storm
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Which simplifies down to...?

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@dusty fox

dusty fox
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Hold on

fair storm
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$y' = 10 : cos x^3 , sin x^5 ,cos x^5 , x^4 - sin x^3 \cdot 3x^2 \cdot sin^2 x^5$

woven radishBOT
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Erebus

dusty fox
fair storm
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YES

dusty fox
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Hih???

fair storm
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That's correct.

dusty fox
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Really

fair storm
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The last part.

dusty fox
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I put the u then v
The answer I'm looking at had v then u

fair storm
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$- sin x^3 \cdot 3x^2 \cdot sin^2 x^5 = - 3 :sin x^3 , x^2 , sin^2 x^5$

dusty fox
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So i did u•v' + u'•v

woven radishBOT
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Erebus

dusty fox
dusty fox
fair storm
dusty fox
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Ok but they had -3sinx² is that correct too?

fair storm
fair storm
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But it should not be the entire last part.

dusty fox
dusty fox
fair storm
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It should contain all

fair storm
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That's the WHOLE second part.

dusty fox
fair storm
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I mean, from this conversation, your idea is correct and your answer is also correct.

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Let me write it out fully

dusty fox
fair storm
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$y' = 10 : cos x^3 , sin x^5 ,cos x^5 , x^4 - 3 :sin x^3 , x^2 , sin^2 x^5$

woven radishBOT
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Erebus

fair storm
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The postioning of the terms?

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You could write $- 3 :sin x^3 , x^2 , sin^2 x^5$ as $- 3 : x^2 , sin x^3 , sin^2 x^5$ or $- 3 : x^2 , sin^2 x^5 , sin x^3$

woven radishBOT
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Erebus

pure flower
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what the hell is going on here

fair storm
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It just depends on your preference.

fair storm
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I'm just hitting all the dialogue options for now.

pure flower
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we have $\dv{}{x} \left(\cos(x^3)\sin^2(x^5)\right)$, yeah?

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lemme rewrite that

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ok.

woven radishBOT
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Περσυ

pure flower
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there we go

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@dusty fox you know product rule

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do you know chain rule

pure flower
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yeah idk what the fuck they did

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that derivative is so wrong

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ok first term is right sure

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whats the second term

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3

fair storm
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Which part was wrong?

pure flower
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..whats the 3.

fair storm
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This part?

pure flower
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what did they do afterwards idek

fair storm
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I think it's about this part here

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They didn't know where to continue, I guess.

pure flower
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weird

pure flower
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like it super doesnt matter

pure flower
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but clean order is $-3\sin(x^3)\sin^2(x^5)x^3$

woven radishBOT
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Περσυ

pure flower
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or maybe $-3 x^3 \sin(x^3)\sin^2(x^5)$

woven radishBOT
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Περσυ

pure flower
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super doesnt matter

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as long as you keep the number at the left

fair storm
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Yep

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A and B same as B and A

devout snowBOT
#

@dusty fox Has your question been resolved?

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charred turret
#

Hey, this is the proof of finding coordinates of a excenter , Im confused at the highlighted part i dont understand how that is true can anyone please help prove the highlighted point

devout snowBOT
#

@charred turret Has your question been resolved?

devout snowBOT
#

@charred turret Has your question been resolved?

lunar harbor
woven radishBOT
#

Civil Service Pigeon

lunar harbor
#

You can also do this with barycentric coordinates if you want to

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pastel rose
devout snowBOT
pastel rose
#

How would I go about proving this ?

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So say I assume N is a normal subgroup of G then show that gng-1 is in N

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But surely that’s just obvious

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Cause of the definition of the normal subgroup

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which is gNg^-1 = {gng^-1 such that g in G and n in N}

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Then the other way, if gng-1 is in N then this just implies that it’s a property of a normal subgroup

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Idk what I’m missing 😭

spark sleet
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What is the definition of normal subgroup that was given in your class? Was it a subgroup N such that gN = Ng, for all g in G?

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If so, you are right, there is almost nothing to do for your exercise, but your writing above is a bit inaccurate

pastel rose
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Not the gN = Ng

pastel rose
spark sleet
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And you use N in the definition itself

pastel rose
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Idk how else to prove this for th exercise

spark sleet
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Can you show the definition of a normal subgroup exactly as it is stated? Assuming you are doing this for a course

spark sleet
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Ok, can you see the difference with the definition and the exercise?

pastel rose
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Exercise has little n

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?

spark sleet
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No, the definition tells you $N$ is a normal subgroup of $G$ if (and only if) $gNg^{-1} = N$ for all $g \in G$. \

The exercise, however, asks you to show that $N$ is a normal subgroup of $G$ if and only if $gNg^{-1} \subseteq N$, for all $g \in G$.

woven radishBOT
#

all matrices are invertible

spark sleet
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In other words, for all g in G, it is sufficient to only check for the inclusion of gNg^{-1} into N, to conclude that N is a normal subgroup.

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Well, this is what the exercise is asking you to prove.

pastel rose
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Oh I see

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OHHH bruh

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Nah that works 😭

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I think I was overthinking it

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lol tysm

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.close

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crude anvil
#

I’m not sure if this is so suitable for this channel, but I am to write up a proof of any geometry theorem using vectors. any suggestions?

devout snowBOT
#

@crude anvil Has your question been resolved?

inland carbon
#

cosine law is a good place to start

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prime vigil
#

how do i determine all the continous function f:D->R where f(2x)=f(3x) for every real x

prime vigil
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i rewrote that as f(x) = f( (3/2)^n * x) for every n natural

harsh sierra
#

hint: take a limit

prime vigil
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for n or for x

harsh sierra
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what do you think

prime vigil
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limit as x aproaches a where a is real?

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ill try that

dire iris
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this is kind of spoiling but you are trying to show that f(x) = f(0) for all x, thus the solutions are the constant functions

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how would you do that with a limit?

prime vigil
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oh

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i understand

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i rewrite

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it as

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f(x) = f((2/3)^n * x

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.closed

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done it thanks

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.close

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weak lichen
#

Hi, can someone help me with this?

devout snowBOT
#
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
devout snowBOT
#

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

rain summit
earnest lagoon
#

1

weak lichen
rain summit
#

if i remember correctly, 1 appears more than other digits as you go along

devout snowBOT
#

@weak lichen Has your question been resolved?

devout snowBOT
#

@weak lichen Has your question been resolved?

shut trail
#

And for the second part.

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As you go farther and faster.

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Consider 11111 and so on.

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You will see that the numbers 1 and 2 will appear more frequently than any other number.

short hare
shut trail
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So no. They don't have a limiting frequency of 1/10

haughty monolith
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Prove it bro

shut trail
# haughty monolith Prove it bro

Best I could come up with is that if you take an interval from 1000-1999. Then all numbers between that interval can be represented as a sum of 1000 + k. if 1 appears only 1/10 of the time. It means that only 1/10 of the numbers starts with 1000. Which implies that 9/10 of the numbers have a number greater than 1999. Which means that between the interval 1000-1999. There's a number, such that 2000 + k = 1000 + k. Which would imply that 2000 = 1000, Which is a contradiction.

(This is the best I could come up with, I know it work for all number 1-9)

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Can't come up with anything better

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😭🙏

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But wait, would it work if you take this approach on every place?

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Oh my fuckin god.

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Not the leading digit.

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AAAAAAAAAAAAAAAAAAAAAAAAA

haughty monolith
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I mean, i don't feel like trying it

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But i'd start by considering the frequency of the digits 0-9 for n-digit numbers

shut trail
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Like. 9 appear 100 times through 1-1000

haughty monolith
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Not sure what kind of pattern you're thinking of making.

shut trail
haughty monolith
#

I mean it's just an exercise in counting

shut trail
haughty monolith
#

You have 100 occurrences for 900-999, sure, but there's at least 101-th appearance in, say, 9 itself

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That's why restricting to digits is probably the right move

shut trail
#

1/10. + 1/100 + 9

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?

haughty monolith
#

I don't understand your question

shut trail
#

Aaaaaaaaaaa

shut trail
haughty monolith
#

9.11?

shut trail
#

Fu

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😭

haughty monolith
#

I haven't done any calculation but I'm almost 100% sure that's not it

shut trail
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Yesh

haughty monolith
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How many 9 digits appear in two digit numbers?

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It's easy: we can start with the 90's

haughty monolith
#

It appears eleven times.

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Then you have seven other starting digits, in which 9 appears once, and the ones, where 9 appears once

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So yeah, 19.

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there's a recursion

#

There ya go.

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severe anvil
#

Theoretically, what would the result be if this did work? Does this even make sense?

severe anvil
#

(such that i is the square root of -1)

severe anvil
#

I am only more confused

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but like theoretically wouldn't it just be 16+30i, because the integral from a to b on 2x is just b²-a² i think

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but also how does this extend to other functions

dire iris
#

think about what it means to go from 0 to 5+3i on the complex plane

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versus going from 0 to 5 on the real number line, for instance

severe anvil
#

still travelling in a line tho right

dire iris
#

well yeah the answer is right in this case, but you cant always just integrate like that

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it doesnt generalize

severe anvil
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oh

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How would it work for another function then, like x²?

dire iris
#

if its path independent, you can essentially integrate normally

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so for f(x) = x^2 it works as well

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so technically it works for almost all functions you would want to integrate, but it doesnt apply to any function

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and its very sloppy in general, because it doesnt give you the proper intuition of what complex integration actually means

devout snowBOT
#

@severe anvil Has your question been resolved?

dire iris
#

if you're curious, i would reccomend you looking at the link riemann posted above

severe anvil
#

i think where we're confused is that im thinking of integrate this function from 0 to x which works normally when x is a real number, so why wouldn't that work if x is complex

dire iris
#

it does work (so long as the function is analytic everywhere)

supple knot
#

You should also read about line integrals first

dire iris
#

yes

supple knot
dire iris
#

@severe anvil integration for functions like this works because the integral is path independent, so you can choose the straight line path from 0 to z, and integrate normally

severe anvil
#

Alright, thanks for the help guys /gen

#

.close

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echo dragon
#

How do I do E

devout snowBOT
echo dragon
#

HELP ME🫩

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And also first one of 2 plz someone help

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I don’t know what to do

rapid merlin
#

What have you tried to solve it

devout snowBOT
#

@echo dragon Has your question been resolved?

echo dragon
coarse flume
#

You know what sin(pi/2) is?

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scenic adder
#

What property/axiom should I cite to justify multiplying by (a - 1) so that the left hand side is divided by (a - 1)?

olive snow
#

Common denominator

#

Actually you rewrite 1 as (a-1)/(a-1)

scenic adder
#

I can see that, for my purposes citing common denominator is good enough

#

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sly oyster
#

What should be the limits?

devout snowBOT
hazy leaf
#

the limits of what?

sly oyster
#

the triple integral, using cylindrical cordinates

hazy leaf
#

oh

#

surely you don't have to triple integral, im not super well-versed in calculus but it looks as if thats excessive

#

my intuition tells me to shuffle the two non-trivial equations to look nicer

sly oyster
#

i dont understand?

sly oyster
restive river
#

where are you stuck?

#

I just studied this in college lol

dire iris
#

no

cloud nymph
#

Mb

sly oyster
#

well the answwer i get from the limits is 96pi but the answer given is 64/3 pi

restive river
dire iris
sly oyster
restive river
sly oyster
restive river
#

for this integral sin must be positive cuz r≥0

dire iris
#

wait yeah i dont get why 96 pi is incorrect

#

that should be the right answer

sly oyster
restive river
#

since r = 8sintheta

#

you can say that this is a circle of radius 4 centered at 0,4

#

and since r is a distance

rare kernel
restive river
#

and cannot be negative

#

r≥0

#

because by definition r is equal to the root of x2+y2

sly oyster
restive river
#

yes

#

that's why -pi/2 gives an incorrect answer

#

try 0 to pi and you'll get the right answer

sly oyster
#

wait a min, i will try

restive river
#

and substitute u = r2

#

mkay I calculated the integrals

#

in cartesian and cylindrical both give the answer to be 96 pi, I believe the book is wrong

sly oyster
#

yeah i did too, its still 96pi

#

okay, ig i will check it with my teacher

restive river
dire iris
#

yeah i think so too

sly oyster
#

np

#

thanks!

restive river
#

mkay

sly oyster
#

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blazing hollow
#

Solve the following equations by using the given substitution. Leave your answers in exact form.

Q1. x^2 + 2x - 2root(x^2+2x) = 3. Let u = rootx^2+2x

Q2. x^2 + x + 12/x^2+x = 8. Let u = x^2+x

thorny bloom
#

show ur work

blazing hollow
#

main focus currently is q1 right now

#

working is up to (for q1

#

u^2 - 2u - 3 = 0
skipping a step
u = 3, -1

wheat pawn
#

$x^2 + 2x - 2\sqrt{x^2+2x} = 3$. Let $u = \sqrt{x^2+2x}$

#

this?

woven radishBOT
#

LordFelix

blazing hollow
#

yep

#

yes

thorny bloom
#

whats the doubt then

wheat pawn
#

okay, so you have u

blazing hollow
wheat pawn
#

so you have two cases, u = 3, and u=-1

#

can you not solve those?

blazing hollow
#

no i'm kinda confused let me type my workkng out

wheat pawn
#

Case 1: $3 = \sqrt{x^2+2x}$

woven radishBOT
#

LordFelix

blazing hollow
#

yep

wheat pawn
#

does this help?

#

can you solve that?

calm blade
#

you need to define u >= 0

wheat pawn
#

no you dont

thorny bloom
calm blade
#

k

wheat pawn
#

what he DOES need to do is check all the solutions of x when he gets them

blazing hollow
wheat pawn
#

can you solve that?

blazing hollow
#

do i use the formula x=-b rootb^2-4ac/2a ?

wheat pawn
#

well, it is a quadratic, right?

mystic scarab
#

Use whatever method you like/have been taught for quadratic equations

blazing hollow
#

okay so would the answer be -1 plus minus root10?

#

i'm trying to figure out if i went wrong or not bc my friend is asleep and her answer is not simular

wheat pawn
#

that sounds correct for case 1

blazing hollow
#

okay thank you

wheat pawn
#

now you need to solve case 2

blazing hollow
#

and for case two i got -2 plusminus root8 over 2

wheat pawn
#

Case 2: $-1 = \sqrt{x^2+2x}$

woven radishBOT
#

LordFelix

wheat pawn
#

and now you need to check all those 4 solutions

#

you have to check that, first off, the original equality holds for those values, and second, that x^2+2x is positive (assuming you're in R)

mystic scarab
blazing hollow
#

u = -1

wheat pawn
#

he's not asking that

blazing hollow
#

wait

#

no i'm going theough my working out sorry

mystic scarab
wheat pawn
#

can the sqrt of a number be negative in R?

blazing hollow
#

i'm so confused rn

wheat pawn
#

okay, let's go to an easier case

#

$-1 = \sqrt{x}$ Is this solvable in $\mathbb{R}$?

blazing hollow
#

what do you mean in r

#

root?

wheat pawn
#

in the real numbers

blazing hollow
#

oh

#

OH

wheat pawn
#

i dont remember the latex code for it

mystic scarab
#

\mathbb{R}

blazing hollow
#

huh

woven radishBOT
#

LordFelix

wheat pawn
#

there we go

blazing hollow
#

i'm so confused can you elaborate on how -1 = rootx^2 + 2x is unsolvable

mystic scarab
blazing hollow
woven radishBOT
#

Alberto Z.

wheat pawn
mystic scarab
wheat pawn
#

it doesnt matter what is inside the root

blazing hollow
#

but how is it the same

wheat pawn
#

the square root of a number is never gonna give you a negative number

#

(in R)

blazing hollow
#

OHHHH

#

thank you very much

wheat pawn
#

so both values obtained from u= -1 are not gonna hold on the original equation

blazing hollow
#

that makes more sense

wheat pawn
#

but you still need to check the values that you obtained from u=3

thorny bloom
#

are we not taking complex numbers

blazing hollow
#

so u can only be -1 plus or minut root 10?

mystic scarab
wheat pawn
#

those CAN be solutions, but you do not KNOW they are until you check them in the original equation

blazing hollow
wheat pawn
mystic scarab
blazing hollow
#

currently in y10 so sorry

mystic scarab
#

Don't worry

blazing hollow
#

y10 tutor math at least

wheat pawn
#

that tells us very little, we dont know your school system

blazing hollow
thorny bloom
wheat pawn
#

okay, so roughly 15-16 age

#

yeah, i would not expect complex numbers yet

blazing hollow
#

thank you guys

wheat pawn
#

you should get to that level in 1 or 2 years probably, but just not yet

#

what i tell my students is that they should keep in mind that those exist, but that we're not gonna use them yet

blazing hollow
#

kill me now

wheat pawn
#

because knowing they exist is helpful for other things, like factoring polynomials

#

so when they get a result where they cant continue, it's because one of those appeared, and they dont need to continue

#

and not because they got it wrong

blazing hollow
#

ohhh okay

wheat pawn
#

that way some theorems are easier for them to understand as well

blazing hollow
#

okay thank you

#

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mellow nest
#

hi, would someone be able to explain how to sketch sinusoidal waves??

hazy leaf
#

you need two things:

  1. the range, or minimum and maximum
  2. the starting state
mellow nest
#

how do you find those??

calm blade
#

Or just plug max and min value of sin and cosx

hazy leaf
#

dont find derivative 💀
do you know the min and max of sin x?

mellow nest
#

is it 2?

hazy leaf
#

is what 2?

mellow nest
#

is max 2 ans min -2

#

wait max 3?

hazy leaf
#

i just want sin(x) lol

mellow nest
#

what the bru

#

wait

#

how do u find max and min

hazy leaf
mellow nest
#

oh

#

max 3 min -1?

hazy leaf
#

yes

#

where does it start? (what is y when x = 0?)

mellow nest
#

start from the middle line?

#

is taht what u mean?

soft umbra
devout snowBOT
#

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surreal orchid
#

Hello

devout snowBOT
calm blade
surreal orchid
#

No

devout snowBOT
#

This channel is only for on-topic discussion. Please take casual conversation to #discussion or #chill.

surreal orchid
#

Ok 👌

calm blade
#

type .close

midnight echo
#

.close

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pastel rose
#

Hi I’m so confused here

devout snowBOT
pastel rose
#

These definitions are too much 😭

#

It’s just saying all the valid outcomes which have a probability of being greater then 0

#

So for the question

#

How can I even think abt it

#

😭

iron sun
#

What is an outcome that has zero probability?

pastel rose
#

According to X

iron sun
#

It could very well happen that some of the fish are not tagged, so the probability of throes outcomes are nonzero and in fact are apart of the support

pastel rose
#

And the probability of a fish being tagged is also non zero

#

Oh wait

#

Unless u get all 10 fish which aren’t tagged

#

Is that 0?

#

Nah no that wouldn’t be

#

That’s still in the support

#

Surely what ever type of fish you get, the chance of that being in the support is 100%

iron sun
#

I think I read ur RV wrong

pastel rose
#

RV?

iron sun
#

X

pastel rose
#

What’s rvx?

iron sun
#

Random variable = RV

pastel rose
#

Ohh

iron sun
#

Okay outcomes in this case are numbers

late pivot
#

Support of X just means the different scenarios of X with non-zero prob.

pastel rose
iron sun
#

So can you come up with an outcome (a number of fishes) that have probability zero?

pastel rose
#

Cause you either get a fish with a tag or a fish without

iron sun
#

There’s only 10 cases here

pastel rose
iron sun
#

Yes

#

X = 0

#

Probability of X = 0 occurring

pastel rose
#

And that’s the support?

iron sun
#

You’ve intuitively already answered the question in some sense

#

Is it possible for X = 11?

pastel rose
#

No

#

Because you only choose 10 fish

iron sun
#

So what’s the support?

pastel rose
#

Ohhh

#

X<=10?

iron sun
#

Yes (integers and >= 0)

pastel rose
#

Ah I have to state integers cause of them being while fish

#

Would I I write that formally?

iron sun
#

X = 0.5 is e.g. also not possible

#

Well what’s the definition of support?

pastel rose
#

Just the support so X = {0,1,2,3,4,5,6,7,8,9,10} ?

iron sun
#

It’s all the x such that P(X = x) > 0

pastel rose
iron sun
#

Yes

pastel rose
iron sun
#

This was already in some sense clear to you before even thinking about the problem I bet

iron sun
pastel rose
iron sun
#

Mhm

pastel rose
#

Now for the probability mass function of X

#

Ik this from definition

iron sun
#

I’d say the key here was to recognise what the outcomes in the first place looked like

pastel rose
#

So give each outcome a probability then

iron sun
#

Not fishes but numbers

pastel rose
#

Oh alright

#

When we say probability mass function what do we actually mean

#

Is it like, in this case for each possible number of tagged fish x, what is the probability that exactly x tagged fish appear in the sample of 10?

#

And the probabilities of each of them summed is 1

#

Hm idk if that even makes sense

#

How would I use ur idea of thinking of them in terms of number rather than tagged fish as

devout snowBOT
#

@pastel rose Has your question been resolved?

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lament schooner
#

Given an almost exact equation here, is it legal to like put the dy and dx back to dy/dx? aka y’

lament schooner
#

Ik we can change y’ to dy/dx and separate but someone told me if we started with dy dx we cant glue it back to y’ idk if it’s true

astral cargo
#

depends

lament schooner
#

On?

wicked rover
stuck star
#

well it depends if the function doesnt change like people in physics do du/dx*dx/dt= du/dt is a lil invalid but moreover in variable separable method (which is the method used to solve the given question) it is allowed

#

which is one of the method that CAN be used*

lament schooner
#

I would just like to know if legal

wicked rover
#

its legal

lament schooner
#

Ty

#

Okay so in every case where you know dy/dx are linked it’s legal right?

stuck star
#

if u can see that y and x terms can be separated do for it

#

to solve a differential equation it is best to form dy/dx first

#

so yes it is legal pretty much

wicked rover
devout snowBOT
#

@lament schooner Has your question been resolved?

lament schooner
#

Ok thanks guys

devout snowBOT
#
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surreal orchid
#

Hello I need help

devout snowBOT
surreal orchid
#

Can someone pls look over this work and tell me if this is correct

#

If not tell me what I did wrong and correct it for me

#

Thxxx

#

Any body

knotty sage
# surreal orchid

could have been done easier by checking that
2 - sqrt(5) = - (sqrt(5) - 2).

surreal orchid
#

What

#

I’m confused

calm blade
#

In original q

surreal orchid
#

Can u show me

#

With the pic I sent u

mighty thicket
#

2 -root5 = (root5 -2).-1

surreal orchid
#

Where in the picture

mighty thicket
#

at the start

surreal orchid
#

Where should I change it

mighty thicket
#

u would have to change the whole proccess shlawg

surreal orchid
#

Im good

mighty thicket
#

yeah

calm blade
surreal orchid
#

Do I just have to change that

mighty thicket
#

no

surreal orchid
#

Will I still end up with the same answer

mighty thicket
#

no

#

u went with the most complicated way lmao

#

u prob got something wrong in the middle of all that stuff

livid geyser
#

The answer he got is incorrect right?

mighty thicket
#

lemme calculate it rq

#

but prob is

#

yeah its wrong

devout snowBOT
#

@surreal orchid Has your question been resolved?

short hare
#

sqrt(5) - 2sqrt(5) is not 3sqrt(5)

#

1-2 = -1 in my book!

#

thats backtracking from the result btw, im not sure if you've made any other mistakes

#

@surreal orchid .

calm blade
#

Op went to sleep

short hare
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fair fjord
#

I'm working on Linear Algebra Done Right 4th edition question 6.A.19:
Given that this is meant to be true for any basis, my intuition is to phrase this question in terms of operations on T and basis vectors. However, I am stuck. Is this approach wrong, or could I have a hint at how to phrase it?

stiff karma
#

Help. FAST, why in 3. Am i getting the line in wrong direction?

#

f(x) = 2-sqrt(1-x)

#

I did the table…

fair fjord
#

this is occupied lol try another

#

<@&286206848099549185>

fickle moat
devout snowBOT
#

@fair fjord Has your question been resolved?

fair fjord
fickle moat
#

Yes, your steps are absolutely correct. Have you thought about trying the Couchy Schwartz inequality next?

fair fjord
#

I'm thinking I need to end up there eventually, but in order for that to get something relevant I need vectors v, w w/ one of <v, w>, ||v||, ||w|| looking like something in the question

#

which is where Im stuck

fickle moat
fair fjord
#

ok so I get that the original sum is the same as $$ \sum_{i=1}^{n} || T\vec{v}_i ||$$ - is this what you mean

woven radishBOT
#

Plaisk

fickle moat
#

That's right

fair fjord
#

OH - so with some eigenvector v of norm 1, we have $<Tv, Tv> = |\lambda|^2$ and these terms are all in the right sum somewhere if we break v up to basis vectors?

woven radishBOT
#

Plaisk

fair fjord
#

nah that doesnt work nvm

fickle moat
#

When you decompose $v$ into basis vectors ($v = x_1 v_1 + \dots + x_n v_n$). We need to prove that the sum of the squared matrix entries on the right is greater than or equal to your $|\lambda|^2$. Then Cauchy-Schwarz inequality to get rid of those $x_k$ coefficients and establish the $\le$ sign.

woven radishBOT
#

ShaddowDagger

fickle moat
#

Since you've already reached this point I think you can handle the rest from here

fair fjord
#

prob eventually! thanks!

fickle moat
#

Im glad I could help catlove

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#

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slate kite
devout snowBOT
slate kite
#

uhh my brain is throbbing cause my friend asked me this question

#

and he has to describe the transformation in words

fair mantle
#

what is the question here exactly

#

do you want g(x) explicitly?

slate kite
#

uhh

#

"describe the transformation in words"

#

and then asking for g(x) explicitly

solar goblet
#

i assume that how each component of g(x) transforms f(x), such as how "-3" transforms f(x)

slate kite
#

the thing that im going insane about is the f(x+1)^2

fair mantle
#

What does the ^2 notation mean in this context? f(x+1)*f(x+1)?

slate kite
#

yeah uhh apparently its not that context as what he's telling me

#

soo yeahhh...

solar goblet
#

i'm going to assume that the notation $f(x)^2$ means $f(x)\times f(x)$

woven radishBOT
#

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solar goblet
#

in my opinion there's really no other way to word the transformation f(x)^2 without just saying it turns the parabolic graph into a quartic-shaped graph

slate kite
#

yeah uhh apparently his answer key says otherwise... its looking at it without the ^2

#

yeah uhh

#

is it just a typo

fair mantle
#

so it's 2f(x+1)-3?

solar goblet
#

without ^2 it looks more reasonable

slate kite
#

uhh apparently thats what the answer suggests...

#

but he is even more confused about this...

#

apparently its x cannot be equal to -1..

solar goblet
#

one question at a time please

slate kite
#

ah mb

solar goblet
slate kite
#

yeah

solar goblet
#

think about what each constant does here, they must be transforming the graph in a way

#

what does multiplying by 2 mean? what does adding 1 to the variable x mean? what does subtracting 3 from the whole function mean?

#

if it helps, play around in desmos

slate kite
#

i know what it actually is without the ^2, was kinda just puzzled by the notation..

#

vertically stretched by a factor of 2 about the x axis, horizontally translating it 1 unit left and vertically translating it 3 units down

solar goblet
#

yup that's the way

slate kite
#

.close

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formal wraith
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formal wraith
#

would it be 4050 instead of 4900 after optimization because it cannot be a square?

#

because the barn takes a side

fossil locust
#

that's correct, cause if the area was 4900, you would need 70 + 70 + 70 + 70

but then 100 metres would be longer than one of the sides

#

I think you might need to check 4500 actually

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echo dragon
#

How do I solve

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woven radishBOT
soft umbra
#

Do you know what unit circle is?

#

@echo dragon

echo dragon
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Yes

soft umbra
#

Can you briefly explain the concept of unit circle?

echo dragon
#

I got to csc 1/sqr5 over 3 but I don’t know where to go from there

soft umbra
#

And after that, try to find the value of k based on the explanation

coral dragon
#

reminder: $cos(\theta) = \frac{\text{adjacent side}}{\text{hipotenuse}} = \frac{2}{3}$

woven radishBOT
#

Tales78945

coral dragon
#

call "adjacent side" as "a" and "hipotenuse" as "h" for better notation 🙂

soft umbra
#

They’re asking csc theta

echo dragon
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3/ sqr5

soft umbra
#

Could you show your work?

echo dragon
#

If u can decipher

soft umbra
#

,rccw

woven radishBOT
soft umbra
echo dragon
#

Answer key is saying the same for b as well

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It’s the reciprocal for some reason

soft umbra
#

okay, I’m confused now

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Are you having problem with a or b

coral dragon
#

I got $\frac{1}{\sqrt{(\frac{3}{2})^2 -1}}$.
@echo dragon did you too?

woven radishBOT
#

Tales78945

echo dragon
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Do I need to simplify that?

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And for B I got 1 over -3/5

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But the answer on the answer key is -5/3

soft umbra
woven radishBOT
#

VerifiedCrank

echo dragon
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1 over (sqr5 / 3)

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Yeah

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Because sin would be sqr5/3 over 1

safe knoll
#

shouldnt u find the hypothenuse thonk

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x and y are adjacent sides and base

echo dragon
#

Isn’t it 1

calm blade
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fierce matrix
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fierce matrix
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.reopen

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fierce matrix
#

∀B,C ∀S,T: Functor(S) ∧ Functor(T) ∧ B, C are groups →
(∃η: NatTrans(η,S,T) ↔ ∃h∈C ∀g∈B, T(g) = h·S(g)·h⁻¹)

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-h->
<-h⁻¹-

g-S->

B--S-->C
|      |
v      v
B--T-->C

g--S-->h

g--T-->h

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trying tto build the diagram and figuring out what this pattern is

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g = h ∘ f ∘ h⁻¹
this is equal g ∘ h = h ∘ f ?

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then this is imilar to the pattern of topological conjugacy

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magic:
g ∘ h = (h ∘ f ∘ h⁻¹) ∘ h = h ∘ f ∘ (h⁻¹ ∘ h) = h ∘ f ∘ id = h ∘ f

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* ──S(g)──> *
|           |
η*          η*
v           v
* ──T(g)──> *

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η* ∘ S(g) = T(g) ∘ η*

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η* = h ∈ C

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T(g) = h · S(g) · h⁻¹

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* ──S(g)──> *
|           |
h           h
v           v
* ──T(g)──> *

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* ──S(g)──> *
|           ^
h           h⁻¹
v           |
* ──T(g)──> *

#

∃ h ∀ g seems like local-global pattern!
h is maybe something global to S and T,
a natural transformation connecting them

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∃ h ∈ C s.t. ∀ g ∈ B = global map
η: S → T = global structure map

#

this seems very similar to how functor is global to arrows

#

.close

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heavy basalt
#

My friend had a question that baffled me.
Suppose we have f(x)=x^2 maped from R to R, can you change it's codomain to make the function injective?
From what we learned in the lessons, in order to make a function injective you need to limit its domain and not codomain.
But my friend suggests limiting the codomain to y<0 or even y<=0, and in both cases the function f(x) seemingly follows the definition of an injective function.
Is my friend correct?

acoustic leaf
#

you can limit the codomain to make a function surjective, but it wouldn't change injectivity

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if you had f(x) = x^2 as a function from R to (negative reals) that wouldn't be a well-defined function, since most inputs would produce outputs not in the codomain

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@heavy basalt Has your question been resolved?

heavy basalt
acoustic leaf
#

every input from a function's domain must be assigned to an output in the codomain

heavy basalt
#

Because the function essentially is just the origin point

acoustic leaf
#

your function must have a valid output for every input in the domain

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if you want to restrict the domain to the origin as well then it works, but otherwise not

heavy basalt
acoustic leaf
#

strictly speaking the domain does not include those values

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e.g. the usual domain for the function f(x) = 1/x would be R \ {0}, the nonzero real numbers

heavy basalt
#

Or am I confusing domain with "preimage" I believe it's called in English?

fierce matrix
#

What about change codomain to 0?

∀x₁, x₂ ∈ ℝ, f(x₁) = f(x₂) → x₁ = x₂
f: ℝ → {0}
f(x₁) = f(x₂) ⟶ x₁ = x₂

¬(x²(x₁) = x²(x₂)=0 → x₁ = x₂) --- oh no it does imply that because the only thing is 0 that can be sent to 0 via x^2, maybe

x²(x₁) = x²(x₂)=0 → x₁ = x₂
∵ ∃!r∈ℝ r²=0, r=0

acoustic leaf
#

there is a notion of "partial functions" where not every point in the domain must have a defined output, but these are not used very often

fierce matrix
#

ℝ---x²--->0

acoustic leaf
fierce matrix
#

Oh wait I don't think my logic holds there

heavy basalt
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So the function 1/x can be mapped from R to R but its domain would be R \ {0}?

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And not R?

acoustic leaf
#

yes, but we wouldn't say it's mapped "from R to R", we would say it's mapped "from R \ {0} to R"

fierce matrix
#

what do you think?

injectivity: ∀x₁, x₂ ∈ ℝ, f(x₁) = f(x₂) → x₁ = x₂
change co-domain to 0: x² : ℝ → 0,
so x²(x₁)=x²(x₂)=0 → x₁=x₂=0
∵ ∃!r∈ℝ r²=0, r=0

acoustic leaf
#

again, you are presupposing the function is well defined in the first place, which is precisely the problem (it is not well defined)

#

also your logic makes no sense, in the third line you just assert it's injective with no proof. i suggest writing out your proof in words

fierce matrix
acoustic leaf
#

that's the definition of injectivity. you have not proven that the function satisfies that definition

fierce matrix
acoustic leaf
#

ok still we have the problem, your function remains not well-defined

fierce matrix
acoustic leaf
#

sure but that's just a different function at that point

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because the formula is f(x) = 0, not f(x) = x^2

fierce matrix
acoustic leaf
#

you can only change the codomain while keeping the same formula as long as the image is a subset of whatever codomain you choose

fierce matrix
#

can we change the codomain of x² : ℝ ⟶ ℝ so it becomes injective?

f : domain ⟶ codomain

codomain change ℝ to 0, f becomes injective

x²: domain ⟶ codomain

x²: ℝ ⟶ ℝ not injective

x²: ℝ ⟶ 0 injective

acoustic leaf
#

you cannot change the codomain of a function (while keeping the same formula!) to make it injective

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only changing the domain can work for that

fierce matrix
acoustic leaf
#

something like that

fierce matrix
#

x ⟼ x² ?

acoustic leaf
#

strictly speaking the same graph, pairs (x,f(x))

devout snowBOT
#

@heavy basalt Has your question been resolved?

fierce matrix
acoustic leaf
#

second one is not a valid graph of a function

fierce matrix
#

but is that not a slightly different concept?
f : ℝ ⟶ ℝ domain codomain are sort of types? so don't have to include all elements

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preimage and image

acoustic leaf
#

all elements of the domain must be included for a relation to be a function

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fierce matrix
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fierce matrix
#

how to change codomain of x^2 : ℝ ⟶ ℝ to make it injective

harsh sierra
#

Change the codomain to the image

topaz beacon
#

dont you want to change the domain

harsh sierra
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Oh right injective

fierce matrix
#

What if you change the codomain to something larger, where source is recorded?

like f⁺ : ℝ → ℝ × ℝ

harsh sierra
#

Yeah so there is no one way to do that

fierce matrix
topaz beacon
#

at that point youre just straight up changing the function

fierce matrix
#

f⁺: ℝ → ℝ×ℝ
f⁺(x) = (x², x)
1 ↦ (1,1)
−1 ↦ (1,−1)
→ injective

stone stump
#

thats not wrong but not the intention

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the idea is to replace the Rs with subsets

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we still want the same formula f(x)=x^2

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Oh I didnt see that you only want to change the codomain. then yeah you'll have to use something like that

harsh sierra
stone stump
#

yeah a bit

harsh sierra
#

Because you make the function injective while forgetting its original structure

fierce matrix
#

you can now ask someone about the same question who can ask someone etc

heavy basalt
#

Damn my question gained some interest

fierce matrix
heavy basalt
heavy basalt
heavy basalt
#

Like there is domain, range, image, and something that relates to domain the same way image relates to range

fierce matrix
harsh sierra
#

While the image is {x>=0}

fierce matrix
#

preimage ⊆ domain
image ⊆ codomain ?

stone stump
#

yes but you should be careful

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there is an image of a function

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there is no preimage of a function

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only a preimage of a set under a function

fierce matrix
fierce matrix
#

Thank you everyone 🙏

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@frank cloud Has your question been resolved?

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@frank cloud Has your question been resolved?

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hearty bison
#

hello anybody need help?

#

i cant read it

#

please

#

type

copper harbor
#

.close

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fossil locust
pseudo basin
#

rip to that

hearty bison
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rough sparrow
#

not a concrete question but why i the fuction f(x)= x^x only defined for postive numbers?

sand dove
#

(-1/2)^-1/2?

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what is that supposed to be

rough sparrow
#

complex for fractions?

#

what about a point like -1/3^-1/3

sand dove
#

?

rough sparrow
#

its discontinious before 0?

unborn osprey
#

yeah

rough sparrow
#

why doesnt atleast show the points that do work?

sand dove
#

well for the points you can define

sand dove
unborn osprey
rough sparrow
#

so its more of computational limitation and to make the fuction easier to understand?

sand dove
#

I guess you can technically define k^k when k is a negative integer

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But when you plot functions on desmos

#

usually the argument is a float type

#

and so there's no good way to define x^x for any those values, even when there are rare exceptions

unborn osprey
#

my teacher told me functions like f(x)=1, when x is rational, 0 when x is irrational
cant be plotted by computers because they change values so rapidly in a discontinuous manner

rough sparrow
#

i see

rough sparrow
sand dove
#

well it's about the float type problem

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here you can only hope to define f(x), x < 0 when x = p/q where q is odd