#help-36

1 messages · Page 278 of 1

final saddleBOT
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@left trail Has your question been resolved?

left trail
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Ok so I choose the u of log (t-1)

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Now the integral that I obtain is $\int_{\log(c-1)}^{\log(x-1)} \frac{e^{2e^u+2}e^u}{u}du$

soft zealotBOT
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BigBen

scarlet sequoia
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wait so u = log(t-1)

left trail
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Yes

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It seemed to be the only way to have t in the denominator

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Oh wait

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I've been confusing myself

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Let me work on the sub again then

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The options seem to be u =t-1 and u= 1/t-1 but both don't seem to lead anywhere

scarlet sequoia
left trail
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Well our bounds are off and the integrand is off

scarlet sequoia
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don't worry about the bounds yet

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let's just focus on integrand

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what is "off" about the integrand?

left trail
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Well to match c) we want e^u. We on the other hand have e^2u+2

scarlet sequoia
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ok

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well, first of all, e^(2u+2) = e^(2u)e^2

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so, up to a constant, it's just e^(2u)/u, right

left trail
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You took the constant out?

scarlet sequoia
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yes, put it in front of the integral

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it's a multiplicative constant

left trail
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Ye I see that but I didn't go past that since c didn't have that

scarlet sequoia
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ok

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anyways

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$e^2\int_{?}^{?}\frac{e^{2u}}{u}du$

soft zealotBOT
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Rafilouyear2026

scarlet sequoia
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what do we need to do now?

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to get e^t/t

left trail
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Let me see what t=2u leads to

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Also why question marks for the bounds? We know the bounda

scarlet sequoia
left trail
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t=2u will get us the correct integrand

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Oh ok. There just c-1 and x-1

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So our integral right now is $e^2\int_{\log(2)}^{2x-2} \frac{ e^t}{t} dt$

scarlet sequoia
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not accounting for constants in front, yes

left trail
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Oh wait right

soft zealotBOT
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BigBen

left trail
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Hmm. I just need to fix the upper bound now. But I cant make a sub since that would ruin our integrand. Does that mean that e^2 will play a role in correcting our upper bound?

scarlet sequoia
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no

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you know exactly what $\int_{\log 2}^{\log x}\frac{e^t}{t}dt$ is for ALL x

soft zealotBOT
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Rafilouyear2026

scarlet sequoia
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you know exactly what $\int_{\log 2}^{\log X}\frac{e^t}{t}dt$ is for ALL $X$

soft zealotBOT
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Rafilouyear2026

scarlet sequoia
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so...

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we just need to find a correct X

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such that the upper bound, 2x-2

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becomes log(X)

left trail
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Oh. e^2x-2

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Wait

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Oh just algebra. x= (2+logx)/2

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But who says we are allowed to choose our x in such a fashion?

scarlet sequoia
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huh

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x and X are different

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you had it earlier

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log(X) = 2x-2

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so X = e^(2x-2)

scarlet sequoia
left trail
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Aren't both of them choosing a specific x and X

scarlet sequoia
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The small x you're working with has been arbitrarily fixed at the beginning

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so you can't change it in any kind

left trail
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Isn't the same with big X?

scarlet sequoia
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No because 28c has already been proved

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so you know, that for ANY x >= 2, that the integral [...] equals Li(x)

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so you're allowed to plug in any value you want

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you can change the name of the variable if you want to

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so you know, that for ANY s >= 2, that the integral [...] equals Li(s)

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now, you can apply it to a specific value, for example s = e^(2x-2), with the fixed x from question d

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and would you look at that

scarlet sequoia
left trail
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Ok I see c) is for any X and we just choose one. The one we choose has another x that is chosen but not given explicitly.

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Thank you for the help

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.solved

final saddleBOT
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final saddleBOT
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patent steeple
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How was a≤c+3 derived?

final saddleBOT
gritty chasm
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$\mathrm{gcd}(b,c) \le c$ right?

patent steeple
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Yes

soft zealotBOT
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Annie Maqionde

patent steeple
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Ok I get it

gritty chasm
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its given $a = \mathrm{gcd}(b,c) + 3$

soft zealotBOT
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Annie Maqionde

patent steeple
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Yes

gritty chasm
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from there you get it

patent steeple
#

Thank you

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final saddleBOT
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sour vale
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Can someone help me with this question. It is related to Arcs

tropic crest
sour vale
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r=9.43

tropic crest
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Now try finding $\angle BOQ$

soft zealotBOT
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multiplexer

sour vale
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Thrugh sin rule right

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32 degrees

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-180

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148 degrees

tropic crest
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Hold up you meant BOA = 32°?

sour vale
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BOC = 32 degrees

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and hten i subtracted 180 to find BOQ right?

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So BOQ = 148 degrees?

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and then i can finmd the arc legnth of the whole PQ which is 29.63

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and find the arc length of BQ now becuase i have the radius and degree

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and i subtracted the arc length of BQ with PQ to find PB

tropic crest
sour vale
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hm im kidna confused

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after i fidn the radius

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I find the angle of BOQ right

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then after i fidn the angle of BOQ i find the arc length og BQ

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and subtract that with hte arc length of PQ

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which will result in just the length oif PB

tropic crest
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wait

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you misread

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you just need to find BQ

sour vale
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ohh nvm thank you thank you

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i understand it now

tropic crest
sour vale
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.close

final saddleBOT
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coral zenith
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<@&268886789983436800>

tropic crest
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<@&268886789983436800>

tropic crest
final saddleBOT
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worldly spruce
strange pelican
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Im better

final saddleBOT
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gentle zephyr
final saddleBOT
drowsy epoch
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skully

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vryh

soft zealotBOT
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Renato

drowsy epoch
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What have you tried

gentle zephyr
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I proved right direction

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need help with left direction

spring haven
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The left direction is easy, just set B=Y

gentle zephyr
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Proof: f(f^-1(B)) = B <=> f surjective

Proof1: f surjective => f(f^-1(B)) = B

(subseteq)
y in f(f^-1(B))
=> there exists some x in f^-1(B) such that y = f(x)
=> there exists some x in X such that y in B
(supseteq)
y in B
=> y in Y
Because f : X -> Y surjective
DEF: forall y in Y, there exists some x in X such that f(x) = y

=> there exists x in X such that y = f(x) in B
=> there exists some x in X such that f(x) in B
=> x in f^-1(B)
=>y = f(x)
=> y in f(f^-1(B))

blissful meadow
gentle zephyr
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first of all, can we modify this direction to make it less messy?

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I did this at like 5am and now that I see it I didnt explained anything and just wrote what I had on my mind

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please dont hold anything back, this proof sucks

blissful meadow
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Hmmmm the argument will remain mostly unchanged. Your proof isn't bad. Maybe you can afford to jump a few steps?\

Like if $y\in f(f^{-1}(B))$, then there is $x \in f^{-1}(B)$ such that $y = f(x)$. From this you instantly have $y \in B$ since $x\in f^{-1}(B)$.\

soft zealotBOT
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Azyrashacorki

blissful meadow
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At the end of the day it's mostly just writing your proof more in words rather than a series of implications.

blissful meadow
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(In fact this direction holds regardless of whether f is surjective or not. If f^-1(B) is empty then f(f^-1(B)) is empty, so it's a subset of B.)

gentle zephyr
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subseteq holds regardless of surjectivity of f but supseteq aswell you say?

blissful meadow
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Oh no sorry I meant like the first inclusion $f(f^{-1}(B)) \subseteq B$.

soft zealotBOT
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Azyrashacorki

gentle zephyr
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because in supseteq i did use that f is surjective

blissful meadow
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Yeah that's what I mean

blissful meadow
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For the other direction you mean?

gentle zephyr
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for the direction f surjective <= f(f^-1(B))

blissful meadow
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Okok

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Well as Kheer suggested, since f(f^-1(B)) = B holds for all subsets B of Y, try to see what happens if you take B = Y.

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This gives you some equality between sets, so you may use it to show that f is surjective.

gentle zephyr
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it does not prove the general case

blissful meadow
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Your claim is $(\forall B \subseteq Y. f(f^{-1}(B)) = B.) \implies (f \text{ is surjective}.)$

soft zealotBOT
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Azyrashacorki

blissful meadow
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So in your premise you're assuming that $f(f^{-1}(B)) = B$ for any $B \subseteq Y$.

soft zealotBOT
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Azyrashacorki

blissful meadow
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This says something useful for the case B = Y, which you can use to show surjectivity.

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So try and see what your premise says about the case B=Y and then try to find a preimage for any y in Y.

gentle zephyr
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again, we are not proving the general case of forall B subseteq Y when we pick B = Y

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you are saying without loss of generality that if we pick B = Y the logic still holds forall B subseteq Y?

blissful meadow
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Your premise says that f(f^-1(B)) = B for any B you want. You know this to be true.

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So in particular f(f^-1(B)) = B when B=Y.

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There is no "without loss of generality" implicit in there.

gentle zephyr
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we are losing generality though

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what if B is a proper subset of Y?

blissful meadow
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The premise is that f(f^-1(B)) = B for ANY subset of Y.

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This necessarily implies that f(f^-1(Y)) = Y.

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This would be true for any subset of Y, but using this you can prove that f is surjective.

gentle zephyr
blissful meadow
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But you're not proving that f(f^-1(Y)) = Y. It's part of your premise.

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You're assuming that f(f^-1(B)) = B for any subset B of Y, and you want to show that this means that f is surjective.

gentle zephyr
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I dont think I follow

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Say for example, we are given that the statement holds for primes p, with forall a,b in N

p | ab => (p | a or p | b)

we are not proving that this is true by showing that p = 2 works

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AH, I see it now, we are not trying to prove this implication, we are trying to prove that assuming this implication holds then f is surjective

blissful meadow
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f(f^-1(Y)) = Y is just a direct result of your premise essentially

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Then from this you can show that f is surjective.

gentle zephyr
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forall y in Y, there exists some x in X such that f(x) in Y?

blissful meadow
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Well from $f(f^{-1}(Y)) = Y$, you can pick $y \in Y$. Then $y \in f(f^{-1}(Y))$. If you expand what it means for $y$ to be in $f(f^{-1}(Y))$, you should be able to find $x \in X$ such that $f(x) = y$.

soft zealotBOT
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Azyrashacorki

gentle zephyr
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forall y in Y, there exists some x in X such that f(x) in Y. In particular there exists some x in X such that y = f(x), then y in f(f^-1(Y))

gentle zephyr
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proving that f is surjective, that is, forall y in Y there exists some x in X such that y = f(x)

gentle zephyr
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I have become quite acquainted with preimages and images of sets as of now, I think I can recite the definition from my memory almost instantly

gentle zephyr
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however the real challenge is using wording for the proof and omitting details that are not explictitly needed in the proof, such as making the proofs self containable as possible

blissful meadow
gentle zephyr
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i will take a break perhaps now

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.solved

final saddleBOT
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final saddleBOT
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chilly raven
#

hwk to simplify

final saddleBOT
south dirge
#

does a have any value or js that?

vital crag
#

,rotate

soft zealotBOT
chilly raven
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wait

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new question

chilly raven
polar spruce
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what have you tried

chilly raven
#

?

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that a and y part is not good

chilly raven
chilly raven
soft zealotBOT
chilly raven
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oye @south dirge

south dirge
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What did you do after x=1??

chilly raven
chilly raven
south dirge
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no i mean after x=1

chilly raven
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log x =0

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x =1

south dirge
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i got tht bhai mera mtlb x=1 likhne ke baad kya kiya

chilly raven
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log x =y log 2=a

chilly raven
#

glt hai shayad

south dirge
#

yeah

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rhs mein 1 kahan se aagya

chilly raven
#

the log x (...)=0

south dirge
#

Okay

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logx kat diya

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uske baad 1 kahan se aagya

chilly raven
south dirge
#

udhar to 0 hi rahega na

chilly raven
#

log x =0
10^0=1

south dirge
#

yeah but log(x*...) nahi hai log(x) * .... hai

chilly raven
south dirge
#

Abhi log ko bhul jao

chilly raven
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ok

south dirge
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tell me smth a (b +c) = 0

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if a isnt 0 then b +c =0 bolna theek hai kya.

chilly raven
south dirge
#

Right

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same cheez idhar

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log(x) * (qwerty) = 0

chilly raven
#

oo

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ok

south dirge
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if log(x) isnt 0 then qwerty =0

chilly raven
#

lekin phir jo maine likha hai usme galat kya hua

south dirge
#

aapne qwerty =1 likh diya

chilly raven
#

oo

#

ok

#

ok

#

.close

final saddleBOT
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chilly raven
#

ty

south dirge
final saddleBOT
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kindred hare
#

loga​b=loga/logb​

final saddleBOT
#

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

kindred hare
#

this is original problem. ArsH, right?

blissful meadow
final saddleBOT
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@kindred hare Has your question been resolved?

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final saddleBOT
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sterile pebble
final saddleBOT
sterile pebble
#

ya so I dont know how to get theta value

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isnt it sqrt(x^2+y^2) for magnitude?

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and arctan y/x for direction

fringe stone
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magnitude of the resultant would be sqrt((∑x)^2+(∑y)^2)

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∑x would be adding the x component of the forces

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so ∑x = Gcosa + F

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∑y would be adding the y component of the forces

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∑y = Gsina

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and the angle theta = arctan(∑y/∑x)

sterile pebble
#

I do not understand these components

fringe stone
#

every force has an x and y component

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like a diagonal line can be broken up into a horizontal and vertical component

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in which if you use pythag on these 2 components you get that force

sterile pebble
#

so g and f give us the force of the pink line

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but why is x Gcosa + F

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<@&286206848099549185>

grizzled atlas
sterile pebble
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final saddleBOT
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short vale
#

can someone help me with linear and exponential handmodeling

barren pebble
#

Do you have a specific problem in mind?

short vale
#

this is all it says for the assignment "linear hand-modeling: justify how to obtain initial value of dataset, slope calculation from 2 points, define all variables and numbers with units;
exponential hand-modeling: justify how to obtain initial value of dataset, relative change per year calculation from 2 points, define all variables and numbers with units;"

heres the data and i need to do it by hand

short vale
final saddleBOT
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@short vale Has your question been resolved?

final saddleBOT
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@short vale Has your question been resolved?

compact laurel
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@short vale Has your question been resolved?

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dense arch
#

“Let P be a point inside a circle. Three distinct chords AB, CD, and EF pass through P. If AB=CD=EF, prove that P is the center of the circle.”

timber leaf
#

Let's draw it out

dense arch
final saddleBOT
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@dense arch Has your question been resolved?

charred agate
timber leaf
charred agate
timber leaf
#

If you don't know then don't say random stuffs here

charred agate
timber leaf
charred agate
#

!done

final saddleBOT
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tall spruce
#

can someone help me

final saddleBOT
tall spruce
#

what is 2+2=

fringe stone
#

4

tall spruce
gritty chasm
#

is this spam

tall spruce
#

im so happy if someone says answer

grave trout
#

It probably is but its a gd reference

gritty chasm
#

not everyone can do that lmao

#

.close

final saddleBOT
#
Channel closed

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fringe stone
charred agate
tall spruce
#

GNG WHAT IS ANSWER I WANNA GET FREE WIFI

gritty chasm
#

<@&268886789983436800>

tall spruce
gritty chasm
gritty chasm
#

hm mods not replying catwhy

stray hill
crude rampart
#

this is a very interesting problem actually

#

once you see the trick, it’s actually quite beautiful, in my opinion

stray hill
#

.close

#

hmm

gritty chasm
#

its closed

stray hill
#

oh already done

#

nice, ty

final saddleBOT
#
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molten zinc
#

guyss solve - Find the domain of the function:- |cos-1(x-4)| + 1/log(3-x)

molten zinc
#

its cos inverse

crude rampart
#

$cos^{-1}(x-4) + \frac{1}{\log{(3-x)}}$

soft zealotBOT
crude rampart
#

is this it?

#

just making sure i read the function correctly

molten zinc
#

yess

brazen breach
# molten zinc its cos inverse

well for the 1/log(3-x), x<3 since the inside has to be positive
cos^-1 can only evaluate for when the inside is between -1 and 1 so
-1__<x-4<1 => 5>x>__3
hence there is no domain or whatever it's called

#

no x value satisfies the solution

#

no real x-value satisfies the equation

#

or gives a real solution idk how to word it

molten zinc
#

well bro i asked for domain not the range of the function

crude rampart
molten zinc
#

its 1/(1+x^2)

#

i think

brazen breach
#

{}

#

wait

crude rampart
# molten zinc its 1/(1+x^2)

no, i think you’re thinking of the derivative , also, that’s not the derivative of arccos assuming you are thinking of derivatives

#

can you tell me what a domain is?

molten zinc
#

{-1,1} i think

brazen breach
crimson pike
brazen breach
brazen breach
#

am I saying this right I can't tell

crude rampart
molten zinc
#

and all function have their own domain

#

i ve got a similar function of which i have already found the domain

zinc verge
molten zinc
#

i think so

#

i am just trying on this one

crude rampart
#

@molten zinc we should start with the basics. what is a domain? can you define it?

brazen breach
molten zinc
#

f ( x ) = cos − 1 ( 2 − | x | 4 ) + ( log e ( 3 − x ) ) like i got the domain of this function

molten zinc
#

[ − 6 , 6 ] this was the answer i got for this one

brazen breach
#

for x__>__3, the inside of the logarithm would be nonpositive hence invalid since the inside of logarithms no matter the base have to be positive

molten zinc
#

it was for the cos part

brazen breach
molten zinc
#

this is the finsl answer [ − 6 , 3 ) − { 2 }

#

f ( x ) = cos − 1 (( 2 − | x |)/ 4 ) + ( log e ( 3 − x ) ) like i got the domain of this function

brazen breach
molten zinc
#

this is the full question that i have solved and got the answer and the first question is my doubt

brazen breach
#

|x| is the absolute value of x

brazen breach
#

there are 2 possible values for |x| for it to be equal to 2

#

-2 and 2

zinc gazelle
#

please help 😭

molten zinc
zinc gazelle
#

😭

#

😭😭😭😭😭😭😭

zinc verge
#

let see

molten zinc
#

but this question is not my doubt

gritty chasm
#

what is your doubt then?

zinc verge
molten zinc
#

my doubt is :- Find the domain of the function:- |cos-1(x-4)| + 1/log(3-x)

#

this is similar to that one

zinc verge
#

ohh

gritty chasm
#

well what have you tried

molten zinc
#

a lot and also diffrentiation

gritty chasm
#

Find the domain of the function:- $|\cos^{-1}(x-4)| + \frac{1}{\log(3-x)}$

gritty chasm
soft zealotBOT
#

Annie Maqionde

gritty chasm
#

and !show

#

!show

final saddleBOT
#

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

molten zinc
#

thats the question

molten zinc
gritty chasm
#

upload it anyways

gritty chasm
#

and explain it as well

zinc verge
#

theres no solution

molten zinc
#

maybe you are right

#

alight then i will close

gritty chasm
#

Please do so.

molten zinc
#

.close

final saddleBOT
#
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final saddleBOT
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rain patrol
#

Hi everyone, I'd like to ask about the significance of Green's functions in the context of solving PDEs.

Here's what I understand, roughly speaking. An example is a Poisson problem $\nabla^2 \phi = f$ (I guess some people put a minus sign but I don't mind). To determine the solution for an arbitrary $f$, we use the Green's function to first solve it for $f = \delta (x - x_0)$ and then integrate the result times the real f over all the $x_0$.

However, I've also seen it used in the context of the heat equation to derive the heat kernel where we are setting not the inhomogeneous term but the initial condition to a Dirac delta. So I guess my question is, where does it go, and how does my Green's function give me the solution?

soft zealotBOT
#

Cark Marney 🐢

final saddleBOT
#

@rain patrol Has your question been resolved?

final saddleBOT
#

@rain patrol Has your question been resolved?

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ancient mural
final saddleBOT
ancient mural
#

Is the question wrong cuz i dont think its solvable with 'different +ve int' (it is a memory based PYQ so.. high chances)

#

I Started with begger's method to get a starting point and then started making cases for 2 same, 3 same.. but that just didnt feel right

royal gust
#

You normally solve these with stars and bars

ancient mural
gritty chasm
ancient mural
#

aight

gritty chasm
#

khan academy or libretext math

royal gust
#

Maybe a different name for the same thing, I don't know beggars method

vital crag
royal gust
#

Yeah they are the same lol

ancient mural
#

they r the same things nvm

#

yea ok but

royal gust
#

Okay so you don't need cases. Consider a different variable u1 = x1 - 2

ancient mural
#

beggers method says nothing about Different +ve integers

gritty chasm
#

or there was this coefficient-in-a-certain-thingy way thing, for this problem i think i'd be coeff of $x^{100}$ in (x^2+x^3...............)(x^1+.......)^3$\\
hm but i dont expect you to know this method, and correct me if im wrong.

soft zealotBOT
#

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

ancient mural
#

i have seen this..

#

wait lemme

gritty chasm
ancient mural
#

i have it in my notes but yk,,, never really saw it

gritty chasm
royal gust
#

That's a useful method if you have a max and min, but with just a min, there's a much easier way

ancient mural
#

no but from what i remember

#

all these never mentioned 'distinct integers case

ancient mural
#

$(\sum_{i=0}^{15} a^i)^3$

soft zealotBOT
#

Chetan???

ancient mural
#

but this too doesnt mention distinct +ve solution

final saddleBOT
#

@ancient mural Has your question been resolved?

final saddleBOT
#

@ancient mural Has your question been resolved?

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sturdy badge
#

I don't understand why im wrong

final saddleBOT
blissful meadow
#

You put parentheses within the parentheses.

sturdy badge
#

oh.

#

.close

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final saddleBOT
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rough nimbus
#

isnt an operation involving a row already being operated on invalid?

royal gust
#

This is valid

#

Note one is happening after the other. They don't happen "at the same time"

final saddleBOT
#

@rough nimbus Has your question been resolved?

heavy plaza
rough nimbus
rough nimbus
versed crater
#

You can think of it as R3 -> R3 - (R2 - R1)

rough nimbus
versed crater
#

ah sorry

#

just do the 2nd one first

#

do R3 -> R3 - R2

#

and then do the R2 -> ... line

rough nimbus
#

that makes sense, thanks for the help

#

.close

final saddleBOT
#
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final saddleBOT
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rustic sable
final saddleBOT
rustic sable
#

wait hold on

#

.close

final saddleBOT
#
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rustic sable
#

i saw it-

#

sorry

rugged merlin
#

fastest help channel

rustic sable
drowsy epoch
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final saddleBOT
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left trail
#

For his proof of theorem 7.2 how can he say that a,b,c are equations involving two polynomials of the same degree. For b and c the Taylor polynomials are not of the same degree

final saddleBOT
#

@left trail Has your question been resolved?

left trail
#

<@&286206848099549185>

rare girder
left trail
#

Ok so what he said is just wrong

rare girder
#

take f(x) = x for instance lol

left trail
#

I'm not seeing the connection?

rare girder
#

let me make sure I understand, is $T_n(f)=\sum_{k=0}^n\frac{f^{(k)}(a)}{k!}(x-a)^k$?

soft zealotBOT
left trail
#

Yes

rare girder
#

ok great, so each T_n(f) is at most an n-degree polynomial

left trail
#

Why at most? It is a n degree polynomial?

rare girder
#

because the nth term may be 0 itself

#

the nth term of the summation in T_n(f) involves taking the nth derivative of f

#

but if f is a polynomial of degree less than n (like a monic polynomial), then that nth derivative is 0

left trail
#

But isn't f always a polynomial of degree n

rare girder
#

f could be exp(-)

#

f(x) = e^x

left trail
#

But an exponential is not a polynomial

rare girder
#

right, thus f is not always a polynomial

#

maybe this is a semantics thing

left trail
#

Ok. But the taylor polyomial will always be of degree n if the nth derivate of f is not 0

rare girder
#

yes

left trail
#

Ok so going back to the question we have Taylor polynomials of n,n+1 and n-1. Clearly they are not the same

rare girder
#

(a) seems fair I think, right?

#

you're adding two <= n-degree polynomials, whose sum is another <= n-degree polynomial

left trail
#

Yes that is but the other two I cant see. And the way he states it makes it seem as though we are applying it for a,b,c. I was worried that I was missing soemthing

rare girder
#

the left-hand side of (b) is the derivative of an <= n-degree polynomial, which is an <= n-1 - degree polynomial

left trail
#

Is it really ≤n since we define it as strictly n

left trail
rare girder
#

the inequality only covers the instance where the functions have n'th derivative 0 at x=0 or x=a for whatever agreed-upon a

#

but like, even in statement (a), f = -g and c1 = c2 could be the case

rare girder
rare girder
#

like if you're saying the claim is false because n-1 is not the same as n, then you could be missing the idea

#

in (a), both sides are degree at most n
in (b), " " at most n-1
in (c), " " at most n+1

#

in either of the three statements, both sides of their respective equation involve polynomial expressions whose degree is bounded by a common number

left trail
#

So your saying it is the same after you apply the integration operator and the differniation operator

rare girder
#

I think I would casually say that this theorem is asserting that T_n is an operator that plays well with addition, differentiation, and integration

left trail
#

Yes I understand that but could his statement be explained then on the left side we have the deirvative of a taylor polynomial of degree ≤n. This of degree ≤n+1 which is the same degree for the one on the right and likewise for the integration

rare girder
#

just to be clear, I don't think the proof in the textbook is satisfactory, it only indicates what the idea is

#

it's easier to just use the definition of T_n in all three statements

left trail
#

Ok so for the first proof I was thinking setting up the polynomial as a sum and simply using the properties of the sums

rare girder
#

yes

left trail
#

The other two proofs I don't know how to formulate rigorously

rare girder
#

just take (b) as an example

#

I don't want to do two things at once lol

left trail
#

So let's say for b. We have a deirvative of a sum. It can be shown by induction that this is equal to the sum of the deirvative

#

So then we are applying the deirvative to each term in the sum and by the power rule this should lower each term by 1. But this to me seems more like an explanation than a rigorous proof.

#

What could I do about that?

rare girder
#

I would address the right-hand side

#

the k'th term in the sum T_(n-1)(f') instructs us to take k derivatives of f'

#

and crucially this is the same as taking k+1 derivatives of f

#

that at least motivates the next step in your proof starting from the left-hand side

left trail
left trail
rare girder
#

I'm saying when you write T_n(f) as a sum

#

like you have
\begin{align*}
\frac{\mathrm d}{\mathrm dx}T_n(f)&=\frac{\mathrm d}{\mathrm dx}\sum_{k=0}^n\frac{f^{(k)}(a)}{k!}(x-a)^k\
&=\sum_{k=0}^n\frac{\mathrm d}{\mathrm dx}\frac{f^{(k)}(a)}{k!}(x-a)^k\
&=\ldots
\end{align*}

soft zealotBOT
left trail
#

Yes I see this. And then we want this to be a sum of n-1 terms where the constant is the same * k(x-a)^k-1.

rare girder
#

it should actually be n terms, but you can write it as n+1 terms all the same

#

you just realize that the first term is 0 and remove it from consideration

#

$\sum_{k=0}^n\frac{\mathrm d}{\mathrm dx}\frac{f^{(k)}(a)}{k!}(x-a)^k=\frac{\mathrm d}{\mathrm dx}\left(f(a)\right)+\sum_{k=1}^n\frac{\mathrm d}{\mathrm dx}\frac{f^{(k)}(a)}{k!}(x-a)^k=\sum_{k=1}^n\frac{\mathrm d}{\mathrm dx}\frac{f^{(k)}(a)}{k!}(x-a)^k$

soft zealotBOT
rare girder
#

because d/dx(f(a)) = 0

#

then you fiddle with indices

#

after taking your derivatives as you mentioned

left trail
#

I see you say j=k-1 and we obtain everything we want in j and simple say k=j

rare girder
#

I like to write reindexing like that in my notes as $k\mapsto k-1$ so that $1\mapsto 0$ and $n\mapsto n-1$

soft zealotBOT
rare girder
#

you are completely right though

left trail
#

Wait for integration shouldn't our sum start from 1?. Since there will be no constant

rare girder
#

no, I'm pretty sure we still must faithfully apply the definitions where they go

left trail
#

We are going to have $\sum_{k=0}^{n+1} \int \frac{ f^{(k)}(a)}{k!} (x-a)^k$

rare girder
#

that seems fine

#

maybe I'm just not seeing the problem because I haven't gone through the motions myself

left trail
#

So each term will gain an (x-a)

rare girder
#

ah, which side is this meant to be?

#

this looks like T_n(g)

left trail
#

Oh so my sum is wrong

rare girder
#

at least if it's meant to be read as the left side

soft zealotBOT
#

BigBen

rare girder
#

I feel like I keep seeing it wrong sorry

#

$T_{n+1}(g)=T_{n+1}\left(\int_0^xf(t)\mathrm dt\right)=\sum_{k=0}^{n+1}\frac1{k!}\left[\frac{\mathrm d^k}{\mathrm dx^k}\int_0^xf(t)\mathrm dt\right]_{x=a}(x-a)^k$

left trail
#

Ok so I take the integral out and I have it for T_n+1

left trail
rare girder
#

because $g^{(k)}(a)=\frac{\mathrm d^k}{\mathrm dx^k}(g(x))|_{x=a}$ with $g(x)=\int_0^xf(t)\mathrm dt$

soft zealotBOT
rare girder
#

that looks a little better to me

left trail
rare girder
#

kinda, the first one does this but not when k=0

left trail
#

Ok makes sense. So for all but k= 0 since it is no derivative.

final saddleBOT
#

@left trail Has your question been resolved?

final saddleBOT
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final saddleBOT
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harsh stratus
#

yo I'm stuck

final saddleBOT
harsh stratus
vital crag
#

nah your antiderivative is wrong

#

$\int \frac{dx}{x} = \ln |x| + C$ yes but not $\int \frac{dx}{f(x)} = \ln |f(x)| + C$

harsh stratus
#

oh

soft zealotBOT
#

riemann

vital crag
#

use exponent rules

#

,tex .exp rules

soft zealotBOT
#

riemann

vital crag
#

then power rule for integrals

unborn cosmos
#

¿Buenas tardes quisiera pregunta,como se desarrolla exactamente los vectores cuando hablamos de fuerza de newtons?

harsh stratus
#

podemos draw vectors like this

#

➡️

compact laurel
plain talon
unborn cosmos
#

a es que soy nuevo gracias👍

vital crag
#

,w int 0 to 1 x/sqrt(x^2 + 1)

compact laurel
vital crag
harsh stratus
#

thank you so much

#

.close

final saddleBOT
#
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loud sundial
#

<@&268886789983436800>

final saddleBOT
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acoustic wharf
#

hi i have a problem:
(67f)^3 = c mod n
with f^3 < n
f is the unknown
to solve this i thought of applying the inverse moduli of 67^3 both sides:
which would give:
f^3 = c
inv(67^3) mod n

acoustic wharf
#

and since f^3 < n

#

f^3 would be equal to c*inv(67^3)

#

but the issue is that last is not a perfect cube

#

where is the mistake in my reasoning

grizzled tusk
#

because you needed c to be a cube mod n (a cubic residue) in the first place

#

(67f)^3 = c mod n means c is equal to a cube mod n

#

then if d is a cubic root of c mod n, ie d^3 = c mod n
f is d*inv(67)

#

you can't tell much more than that if you don't give a n and a c

final saddleBOT
#

@acoustic wharf Has your question been resolved?

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gentle zephyr
final saddleBOT
gentle zephyr
#
  1. Prove that for all $n \in \mathbb{N}$ it holds that $36 \mid 19^n - 18n^2 - 1$.
soft zealotBOT
#

Renato

gentle zephyr
#

6 | 36 => 6 | 19^n - 18n^2 - 1

#

19^n - 18n^2 - 1 = 1^n - 0 - 1 = 0 (mod 6)

#

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turbid bramble
#

I’m not sure if I got the graphing correct I also don’t know how to find the b value

turbid bramble
tame cipher
#

spam vs skill

tame cipher
#

LOLOLOL

turbid bramble
tame cipher
#

SON😭😭😭😭😭😭😭😭😭😭

turbid bramble
#

No seriously I need help

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How do I find the b value

gritty chasm
tame cipher
gritty chasm
#

!original

final saddleBOT
#

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

final saddleBOT
turbid bramble
#

Idk the name

gritty chasm
#

Post the original question, please.

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With full context

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If it's not in english, translate

turbid bramble
gritty chasm
#

so what you are graphing is $y = 2\cos \theta + 1$

soft zealotBOT
#

Annie Maqionde

tame cipher
#

yes

turbid bramble
#

Yes

gritty chasm
#

If I were you I'd take 5 values of $\theta$ and find the corresponding values of $y$, make a table, then plot.

soft zealotBOT
#

Annie Maqionde

gritty chasm
#

5 cuz it says so in the question

tame cipher
#

wait lemme try to make a table

gritty chasm
#

Since this is not your help channel

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Please don't interrupt

turbid bramble
#

We’re in the same class sorry

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That’s why they’re here

gritty chasm
#

It doesn't matter.

tame cipher
gritty chasm
#

Required person will copy from the OP later.

turbid bramble
#

Thanks for the help

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warped herald
final saddleBOT
warped herald
#

how do I start

gritty chasm
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Well I may give some hint on (ii)

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Try to show something is congruent

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hint semicircle subtends right angle

warped herald
#

as in b?

gritty chasm
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yes. sorry

warped herald
#

so here

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I joined OQ

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so the angle at the centre is twice the angle on the circumference

gritty chasm
#

which qs? a, b or c?

warped herald
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for b

gritty chasm
#

no try to show QRP and SRP are congruent

warped herald
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radius and common side matches

gritty chasm
#

look at the angles

warped herald
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so QR is the bisector

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so angle PQO and SQO equal

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meaning POR and SOR too

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that’s it right?

gritty chasm
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observe RQP=RSP = 90 degrees

warped herald
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yea

gritty chasm
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and QRP = SRP

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and theres a common side RP

warped herald
#

yes

warped herald
#

because of the bisector?

south dirge
#

Yeah

gritty chasm
#

yes

warped herald
#

ok

final saddleBOT
#

@warped herald Has your question been resolved?

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flint ibex
#

can someone explain

final saddleBOT
flint ibex
#

where the minus comes from

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what i did was

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sechy=x/2

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differentiate with respect to x

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dy/dx(sechy multiplied tanhy) = 1/2

rocky tusk
#

you’re missing a - and also the derivative of x/2 is not x/2

sly forum
sly forum
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it is function of x in terms of y

flint ibex
#

but where is the minus coming from

rocky tusk
#

derivative of sechy

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dy/dx (-sechy tanhy)

flint ibex
rocky tusk
#

this isn’t sec

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it’s sech

flint ibex
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i dont see why it doesnt stay the same cos of the hyperbolic function

sly forum
flint ibex
#

i know abt the one rule

flint ibex
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if u have like sinh^2 x u put a negative

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infront

rocky tusk
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refer to the exponential definition

flint ibex
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but like most the time it randomly doesnt apply

rocky tusk
#

sec and sech aren’t the same function

flint ibex
#

but most the derivatives of the normal function are the same

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as its hyperbolic

rocky tusk
#

instead of just assuming the same rules from trig work for hyperbolic just use the exponential definition and figure it out yourself

flint ibex
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this is a past paper dw

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but still

rocky tusk
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you do

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it’s quite simple

sly forum
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or yea just do it once

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and you will remember it everytime a question comes up

flint ibex
#

yh fair point

flint ibex
#

thank you

#

but do any of you abt the one rule

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where if u have sinh^2x u put a negative in front

sly forum
flint ibex
#

its like why it goes from cos^2+sin^2=1 becomes cosh^2-sinh^2=1

sly forum
#

not the

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regular

final saddleBOT
#

@flint ibex Has your question been resolved?

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dry path
#

What do you call these things in the calculator? Referring to "x10²⁷." There are some cases where that's also a negative (e.g. x10^-03). What actually are they and how do they work?

Do they have a specific term or name?

formal trail
#

it's scientific notation

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it's literally multiplying by 10 raised to that power

dry path
#

Ohhh okay then, thank you! Just wanted to make sure

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proper lion
#

<@&268886789983436800>

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proper lion
#

also who removed my true role

tropic crest
proper lion
#

😡

#

who did

formal trail
#

true and false roles generally only last 1 day

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potent nova
#

Hi How do you do this no calc?

final saddleBOT
severe canyon
#

Integrals without calc? 🤔

sturdy cypress
#

yeah, if you do an integral that was calc

timber leaf
#

It's indefinite integral anyways

chilly pollen
quiet python
#

They might mean without a calculator

timber leaf
#

Elderly won't get this slang

sturdy cypress
#

calculators can;t do this as whipl said

quiet python
#

Wolfram Alpha is a calculator that can solve it, im assuming there will be various other ones that can as well

worldly spruce
#

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

soft zealotBOT
worldly spruce
#

Use this

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@potent nova

timber leaf
#

Then it can be splitted into two smaller integrals, smart

final saddleBOT
#

@potent nova Has your question been resolved?

potent nova
potent nova
#

to make integrals

worldly spruce
#

You might want to react to the bot

potent nova
#

I still dk jow to solve it

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i tried the identity and it still didnt work

final saddleBOT
#

@potent nova Has your question been resolved?

potent nova
#

??

slate crater
#

ngl i lurked theough the server and found ur integral and ive been trying stuff for a while but i cant get anywhere either 💀💀🥀

#

if only it were from 0 to π/2...

timber leaf
#

$(1-\cos(x)^2)\cdot \cos(x)^4$

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This should help

soft zealotBOT
timber leaf
#

@potent nova @potent nova

slate crater
#

ik the solution (or one ig) from a calculator app i got and gaw damn

timber leaf
#

!nosols 😭

final saddleBOT
#

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

coral zenith
#

its a lengthy integral anyways

worldly spruce
#

How in the world did you get that

slate crater
worldly spruce
#

You are done in like 6 steps, I don't know what's the problem

timber leaf
slate crater
#

hell yeah 🔥🔥🔥

timber leaf
#

But anyways by expanding the cosines and split it out it wont be that bad

slate crater
#

i mean if u go from sin²cos⁴ to cos⁴-cos⁶ and manip a bit u end up with (sincos)²dx idk 🥀🤠

slate crater
#

maybe im just making errors

worldly spruce
#

Show your work

timber leaf
#

She is not OP

worldly spruce
#

Oh

timber leaf
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My skibidi blud

slate crater
#

tbf i might aswell by the second OP LMFAO

#

cuz im also having trouble 🥀💀

timber leaf
#

I dont think the question is that bad

coral zenith
slate crater
#

thats what i thought snd why i tried doing it in order to help w a hint

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but erm

worldly spruce
#

Power reduction

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A bit of manipulation

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Done

timber leaf
#

Or cos^6 =cos^4cos^2

worldly spruce
#

Sure

slate crater
#

yeah w it is just straight forwars

brazen breach
brazen breach
slate crater
slate crater
final saddleBOT
#

@potent nova Has your question been resolved?

worldly spruce
#

I meant the power reduction identity for cos^2(x)

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(1+cos(2x))/2

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"they can't trust"

#

It seems the OP has no intention of solving this anyway ...

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mint forum
#

hi guys im really confused on how to proof by contradict its just a hard concept for me, and i was wondering if you could check if my answer is right and i didnt know whether to say " asuume that m^2 is not divisible by 2 or that m is not divisible by 2"

vital crag
#

the proof should start with the negation of the conclusion. The statement in question has the form
if P then Q

#

where P is the statement $m^2$ is divisible by 2. and Q is the statement $m$ is divisible by 2.

soft zealotBOT
#

riemann

mint forum
#

Oohh okay

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so you negate Q?

vital crag
#

The negation of Q is the negation of m is divisible by 2

mint forum
#

And is that always the case?

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Where it says if P then Q

vital crag
#

for proof by contradiction yes

mint forum
#

Just negate Q alwyas

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WOWWWWWW OMG

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Wait let me find a new question just to test this

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Sorry, what about these two?

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these dont have the if P and Q so for example, the 2nd one i'll just say "assume that there are positive integers for p and q"

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but for the first one i make sure that tanx - sinx < 0?

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so like flip the sign orrr

vital crag
#

how about you focus on one problem at a time and write out your "if P then Q" here

vital crag
mint forum
#

Okay so, for this question, "if tanx - sin x > 0 within 0 < x < 90, then tanx - sinx > 0 within a different range?"

whole lion
mint forum
#

Icl this ones hard idek wht im saying

mint forum
whole lion
#

ok

whole lion
#

note that, a perfect square when modulo 3 is either 0 or 1

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4p^2 - q^2 = p^2-q^2 = 2(mod 3)

mint forum
whole lion
#

what do you mean

mint forum
#

like where have u gotten that from

whole lion
#

you consider 3 cases: x modulo 3 is 0 1 or 2

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i mean my english(in math) sucks

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forgive me

mint forum
#

ok so first are we provin that there are no positive integers for 4p^2 - q^2 =25

mint forum
#

which is like senior year

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so i dont wanna overcomplicate it

whole lion
#

i'm 14yrs old

mint forum
#

💀 oh damn

whole lion
#

it's kind of basic knowledge you know

mint forum
#

yeah i just got humbled

whole lion
#

the system in my country is kinda complicated

mint forum
#

Yeahh maybe you're asian lol

#

Really smart

whole lion
#

you got it right 🙂

mint forum
#

🤣 Could tell

whole lion
#

p^2 is divisible by 3 and 3 is prime so p is divisible by 3, which means p = 3

#

wait

#

oops

blissful meadow
#

It's probably more straightforward at this level to factor 4p^2 - q^2 and consider factors of 25.

whole lion
#

lemme rethink for a bit

mint forum
#

Thank you tho logic guy

whole lion
#

sry for overcomplicating things

mint forum
#

So like i factor out 25 for 5 x 5

blissful meadow
#

Then try to factor 4p^2 - q^2. Should be an identity you've seen before.

mint forum
#

idk is it like difference of 2 squares

#

Omg yayyy

#

is it like that

blissful meadow
#

Yep