#help-49

1 messages · Page 105 of 1

midnight plankBOT
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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
twilit field
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0.5

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oh

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oops

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4

placid spoke
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sure lol

twilit field
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$bc=ak_1$.
\
We now divide across by $c$
\
$b = \frac{ak_1}{c}$

strong lava
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ew, fractions in my arithmetic class?

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disgusting

grand pondBOT
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A dense set

twilit field
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Have to figure out how gcd(a,b)=1 is relevant here

placid spoke
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what is the proposition mentioned?

strong lava
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what does the proposition on page 152 say

twilit field
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bezouts

placid spoke
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oh perfect

strong lava
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wow

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imagine not naming it

twilit field
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so 1=ak+bl

placid spoke
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here's the hint that makes everything fall together: multiply both sides by c

twilit field
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$1=ak+\frac{ak_1l}{c}$

grand pondBOT
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A dense set

twilit field
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I now multiply across by \frac{c}{a}

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to get $\frac{c}{a}=k+k_1l$

grand pondBOT
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A dense set

twilit field
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Which proves $a \mid c$

grand pondBOT
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A dense set

placid spoke
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a bit convoluted but it works sure

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nothing you did was wrong

twilit field
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wish I had thought of this

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bezouts would have never struck me

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$ab=pk_1 \implies b= \frac{p}{a}k_1$

grand pondBOT
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A dense set

twilit field
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wait

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oops

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I was accidentally proving a\mid p and b\mid p

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We prove the contrapositive, if $p \nmid a$ and $ p \nmid b$ then $p \nmid ab$

grand pondBOT
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A dense set

twilit field
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$a=pq_1+r_1; 0<r_1<p$
\
$b=pq_2+r_2;0<r_2<p$
\
It thus follows that $ab= p^2q_1q_2+pq_2r_1+pq_1r_2+r_1r_2; 0<r_1r_2<p^2$
$r_1r_2 \neq p$ as that would require one of $r_1$ or $r_2$ to be p
\
It thus follows that $ p \nmid ab$

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How does this look?

grand pondBOT
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A dense set

twilit field
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How does this look?

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Is this fine?

jaunty canopy
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so you've found an expression for ab

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ab = p*stuff + r1r2

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but you've said that in order for r1r2 to be divisible by p, that would mean r1 or r2 is divisible by p

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which is circular cus that's exactly what we're trying to prove

paper inlet
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bro just stop if you keep swimming in lead rivers you will turn into stone

jaunty canopy
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why does r1r2 = p?

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why is it not the case r1r2 = 2p?

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btw i've got my galois theory supervision now

jaunty canopy
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also <@&268886789983436800> please can u deal with this

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if you don't have anything useful to add please stop spamming the chat

twilit field
twilit field
grand pondBOT
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A dense set

twilit field
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<@&286206848099549185>

shy marsh
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you want to prove euklids lemma?

twilit field
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no

twilit field
shy marsh
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this is euklids lemma

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In algebra and number theory, Euclid's lemma is a lemma that captures a fundamental property of prime numbers:

For example, if p = 19, a = 133, b = 143, then ab = 133 × 143 = 19019, and since this is divisible by 19, the lemma implies that one or both of 133 or 143 must be as well. In fact, 133 = 19 × 7.
The lemma first appeared in Euclid's El...

twilit field
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I know

shy marsh
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ok, so you want to prove this elementary right (without prime factorization)?

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or what do you need exactly?

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ok you want to continue your proof i guess

twilit field
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yes

shy marsh
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you got p|r_1r_2

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the idea is now that you can keep reducing mod p, do you have an idea how?

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like you know r_1,r_2<p also

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and assume that r_1r_2>p

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then consider the minimal k such that r_1*k>p

twilit field
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I would like to understand why my proof is wrong

shy marsh
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no your proof is just incomplete i think

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cuz what if r_1r_2=rp

twilit field
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Well, that's not possible

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as $r_1, r_2 \neq p$

grand pondBOT
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A dense set

shy marsh
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yeah but you are using here the lemma which you try to prove

twilit field
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hmm

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I'm not convinced

shy marsh
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like why cant it be that $$r_1\cdot r_2 = 2p$$ with $r_1,r_2 \neq p$

grand pondBOT
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cosmic

twilit field
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again, that would require r_2 =p

shy marsh
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why, you are using here that the Z is a UFD, which we havent proven yet cuz this proof relies on this lemma

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like we dont know that the primefactorization is unique yet

twilit field
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oo

shy marsh
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like there are rings where this is false

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so you have to still prove this for the integers

twilit field
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I literally had to prove soemthing relating to dual sided ideals today lol

shy marsh
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so you have to use something specific to integers, and that are often size arguments

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i have to leave now unfortunatelly, sorry hope it helped a bit at least

twilit field
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Thanks!

midnight plankBOT
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twilit field
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midnight plankBOT
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obtuse totem
midnight plankBOT
obtuse totem
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how did they find the general solution?

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cause we learnt a method in which constants are infront of y”,y’ and y

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what do you do if it’s not a constant in front?

thorny coyote
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Trial solution of y=X^n

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Its just something u remember, when it has x infront u just try that

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P much it

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its also like in the screenshot u sent, u go from the equation to the characteristic equation by using a trial soln of y=e^rx

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you just suggest a trial solution

midnight plankBOT
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@obtuse totem Has your question been resolved?

obtuse totem
thorny coyote
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Yea

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try it on some rough paper it works out

obtuse totem
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n as in the highest degree of x?

thorny coyote
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No just a constant

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when u sub in the trial soln y=x^n into that first image equation, youll find an equation which leads to n=2 and n=-2 which leads to ur general soln

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Try it out trust its easier to understand

obtuse totem
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ok

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thank you

midnight plankBOT
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@obtuse totem Has your question been resolved?

thorny coyote
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u got it?

obtuse totem
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yes!

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midnight plankBOT
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dreamy tapir
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yooo

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help

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.reopen

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BRUH

midnight plankBOT
#
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potent fractal
midnight plankBOT
potent fractal
#

I know how to do this question but I don't understand why my method doesn't work

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I tried doing this to get
1/244sin(60) for 4sqrt3
I also got 60/360
pi*4^2 =8/3 pi for the sector

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Do when we consider a quarter of a circle, it is 4pi
so the shaded area for 1/4s of a circle is

4pi-(8pi/3+(8pi/3-4sqrt3))
4pi-16pi/3+4sqrt3

=4pi-16pi/3+4sqrt3

so in the whole circle,
16pi-64/3pi+16sqrt3
= -16pi/3 + 16sqrt3

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which is correct

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nvm I played myself

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potent fractal
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.reopen

midnight plankBOT
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potent fractal
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the answer is indeed -16pi/3 + 16sqrt3 but I did a step wrong

potent fractal
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midnight plankBOT
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oak rain
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Help me with parabolas

midnight plankBOT
oak rain
midnight plankBOT
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@oak rain Has your question been resolved?

oak rain
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No it hasn’t but im uses to it so I might leave the server

midnight plankBOT
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@oak rain Has your question been resolved?

oak rain
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Still no, no one fucking helps me

daring bison
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can u take another pic of the questions

midnight plankBOT
#

@oak rain Has your question been resolved?

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livid seal
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Guys help my homework 😭

midnight plankBOT
livid seal
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<@&286206848099549185>

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keen seal
midnight plankBOT
keen seal
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for b

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in the theorem

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its not very pythagorean like

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oh

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<

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nvm

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midnight plankBOT
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twilit field
midnight plankBOT
twilit field
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Trying to prove this

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$dim(V)=dim(null(T)) + dim(range(T))$

grand pondBOT
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A dense set

twilit field
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Let the nullity of $T$ be $r$.Let $dim(V)=n$ Let the basis of $null(T)$ be ${e_1,e_2,\dots,e_r}$. This basis can be extended to one of $V$ , giving $\beta ={e_1,\dots,e_r,f_1,\dots, f_{n-r}}$.
\
We now show that $dim(range(T)) = n-r$. To do so we consider an arbitrary vector, spanned by $\beta$.
\
$v = a_1e_1+ \dots a_re_r+b_1f_1+b_2f_2+ \dots b_{n-r}f_{n-r}$
\
$T(v) = T(\sum_{i=1}^{n} a_ie_i + \sum_{i=1}^{n-r} b_iT(f_i)$
\
$T(v)= \sum_{i=1}^{n-r} b_iT(f_i)$
Let's suppose these vector weren't linearly independent.
\
in that case there exist non-zero scalars such that
\
$T(\sum_{i=1}^{n-r} b_iT(f_i))=0$
\
This would imply $\sum_{i=1}^{n-r} b_iT(f_i)$ lies in $null(T)$.
\
This is obviously absurd, as the vectors in the span of $f_i$ don't belong to null(T). we've thus arrived at a contradiction.
\
\
From that, we can conclude that $dim(rnage(T))= n-r$
\
From this the desired result is evident

grand pondBOT
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A dense set

twilit field
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I feel this is missing something though

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Let the nullity of $T$ be $r$.Let $dim(V)=n$ Let the basis of $null(T)$ be ${e_1,e_2,\dots,e_r}$. This basis can be extended to one of $V$ , giving $\beta ={e_1,\dots,e_r,f_1,\dots, f_{n-r}}$.
\
We now show that $dim(range(T)) = n-r$. To do so we consider an arbitrary vector, spanned by $\beta$.
\
$v = a_1e_1+ \dots a_re_r+b_1f_1+b_2f_2+ \dots b_{n-r}f_{n-r}$
\
$T(v) = T(\sum_{i=1}^{n} a_ie_i + \sum_{i=1}^{n-r} b_iT(f_i)$
\
$T(v)= \sum_{i=1}^{n-r} b_iT(f_i)$
Let's suppose these vector weren't linearly independent.
\
in that case there exist non-zero scalars such that
\
$T(\sum_{i=1}^{n-r} b_iT(f_i))=0$
\
This would imply $\sum_{i=1}^{n-r} b_iT(f_i)$ lies in $null(T)$.
\
This is obviously absurd, as the vectors in the span of $f_i$ don't belong to null(T). we've thus arrived at a contradiction.
\
\
From that, we can conclude that $dim(rnage(T))= n-r$
\
From this the desired result is evident

grand pondBOT
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A dense set

twilit field
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Is this fine?

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<@&286206848099549185>

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.close

midnight plankBOT
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midnight plankBOT
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coarse agate
#

does anyone know how the ford-fulkerson algorithm works under graph theory? 🥹

midnight plankBOT
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@coarse agate Has your question been resolved?

coarse agate
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<@&286206848099549185>

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here's the iterations I've done but I'm not sure if I did something wrong or is this okay already 🥹

midnight plankBOT
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coarse agate
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sacred musk
#

hey guys I have a calc 3 midterm worth 50% of my grade tmr and the professor didnt explain this topic ive spent like 5 hours trying to understand can someone help me pls?

I need to be able to change the order of integration to dydzdx and dydxdz:

sacred musk
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it gets super weird and the answer doesnt make sense to me

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a GSI basically said its gonna be on the test tho and im kinda panicking

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better picture of the integral

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(ive drawn many pictures)

tall lotus
grand pondBOT
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deepfriedrich

sacred musk
tall lotus
grand pondBOT
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deepfriedrich

sacred musk
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it has nothing to do with integrating its just showing you know how to manipulate bounds

tall lotus
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Oh, my bad I did not see that.

sacred musk
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but the only ones I struggle with are dy[dxdz,dzdx]

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getting dy first and satisfying the inequalities proves tricky

midnight plankBOT
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@sacred musk Has your question been resolved?

last slate
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can u draw the region

midnight plankBOT
#

@sacred musk Has your question been resolved?

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civic lagoon
#

The problem is here

midnight plankBOT
civic lagoon
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What's the next step? 🙏🏼

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I don't understand the way it explained here

tall lotus
civic lagoon
tall lotus
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Is this the entire question?

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@civic lagoon

civic lagoon
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Yes

civic lagoon
tall lotus
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Happens.

civic lagoon
tall lotus
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Ah, I'm not good at reading handwriting but I can try.

civic lagoon
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Ok

tall lotus
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nothing more than that.

civic lagoon
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like what?

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hwat

tall lotus
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Like cancel out x from numerator and denominator

civic lagoon
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so the x^2 from the numerator will be gone?

tall lotus
civic lagoon
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So how do I get the second form?

civic lagoon
tall lotus
civic lagoon
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Like this?

tall lotus
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No.

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Like this
$x(x(2e^{2x}-2e^{-2x})+2e^{2x}+2e^{-2x})$

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You can do differentiation, this shouldn't be a big deal, right?

civic lagoon
tall lotus
civic lagoon
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Ohhh

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Yes I can

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Where did the 2x go?

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✋🏻😭

tall lotus
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I missed the 2, my bad.

grand pondBOT
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deepfriedrich

civic lagoon
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so the x^2 is the x(x?

tall lotus
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$\frac{x(x(2e^{2x}-2e^{-2x})+2e^{2x}+2e^{-2x})}{x^4}$\
\
$\frac{2xe^{2x}-2xe^{-2x}+2e^{2x}+2e^{-2x}}{x^3}$

grand pondBOT
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deepfriedrich

civic lagoon
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Ohhh

tall lotus
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Then you take 2x common and simplify further.

civic lagoon
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ok ok

tall lotus
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$\frac{2(e^{2x}(1+x)+e^{-2x}(1-x))}{x^3}$

grand pondBOT
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deepfriedrich

tall lotus
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This is after clubbing e^{2x} and e^{-2x} terms together.

civic lagoon
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Oh okk

civic lagoon
tall lotus
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See what terms have e^{2x} multiplied to them

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2xe^{2x} and 2e^{2x}

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Then take e^{2x} common

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e^{2x}(2x+2)

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2e^{2x}(x+1)

civic lagoon
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I still don't get it, I'm sorryyy.

tall lotus
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I can't spoon-feed harder than this </3

civic lagoon
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Okkk

tall lotus
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Can you understand this:
$ab+bc = b(a+c)$

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@civic lagoon

grand pondBOT
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deepfriedrich

civic lagoon
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Yes

tall lotus
tall lotus
civic lagoon
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Ok

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Thank youu

midnight plankBOT
#

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barren onyx
midnight plankBOT
steep hinge
#

it is like the number of positioning 6 object in 6 different places

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divided by the number of symmetries that the cube has

storm spindle
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The 6! Is right

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But there are more than 6 rotational symmetries of a cube

storm spindle
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Well each of the six sides can be up top

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But for each side being up top you can rotate the cube along its vertical axis

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4 times

barren onyx
steep hinge
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A position of the cube is defined by bottom face and a rotation of the z-axis

storm spindle
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With then different faces being in the front each time

steep hinge
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so it seems like 6*4

barren onyx
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yea

storm spindle
barren onyx
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so every side is symmetrical to other

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then how is it not 6*6

storm spindle
barren onyx
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After rotating

storm spindle
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Yeah, you’re keeping the cube itself the same

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Like rotating a die

barren onyx
#

in our solution it is given as 5*3!

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and the hint says use circular permutation

storm spindle
barren onyx
barren onyx
storm spindle
# barren onyx this is what it says

This is basically the comprised version of the 6!/24 explanation.

We say we start with the first color. For the opposite face there are 5 colors and for the other for there are 3! Ways to do it. Since the starting color doesn’t restrict our options, 5*3! Must be the solution

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I don’t really like that explanation though, I find it too unconvincing

barren onyx
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how is it 1

storm spindle
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You start with the first color, not the first side

barren onyx
storm spindle
barren onyx
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Doesn't allows to use different methods

storm spindle
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Damn it okay

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Strange fella

barren onyx
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🤡

barren onyx
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and not 4!

storm spindle
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Yeah there they just said 4! Divided by the 4 circular symmetries

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Which is 3!

barren onyx
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ohh

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thanks @storm spindle

storm spindle
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Yw

barren onyx
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have a good day

storm spindle
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You too

barren onyx
#

.close

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twilit field
#

I want to prove the following lemma

midnight plankBOT
twilit field
#

$cgcd(a,b)=gcd(ca,cb)

#

I think I can use bezouts?

storm spindle
#

I actually have a nice proof of this at hand

#

Well actually, only in one direction i suppose

twilit field
#

As in cgcd(a,b) \geq gcd(ca,cb)

grim vector
twilit field
#

or something like that

storm spindle
#

May be a bit restricted though, depending on what you’re allowed to assume

visual tiger
#

take $d = gcd(a,b)$ and $D = gcd(ca,cb)$

grand pondBOT
#

rafilou is not not born in 2003

twilit field
#

Yeah, I know how to do that I think

visual tiger
#

we know d|a and d|b, so cd|ca and cd|cb

#

cd|D

twilit field
#

For bezouts, I was thinking $k_1a+k_2b = gcd(a,b)$

grand pondBOT
#

A dense set

twilit field
#

we now multiply across by $c$ to obtain

grand pondBOT
#

A dense set

twilit field
#

$k_1ca+k_2cb=cgcd(a,b)$

grand pondBOT
#

A dense set

twilit field
#

but k_1(ca)+k_2(cb)=gcd(ca,cb)$ for some choice of $k_1,k_2$

grand pondBOT
#

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

twilit field
#

therefore $gcd(ca,cb)=cgcd(a,b)$

storm spindle
grand pondBOT
#

A dense set

twilit field
#

the problem we run into is proving that the K_1, k_2 are the same

visual tiger
#

alternatively, you could use the fact that the gcd is the only common divisor that can be written as a linear combination

#

for d >= 0, d = gcd(x,y) <=> d|x, d|y and d = ux+vy

twilit field
#

Hmm

twilit field
twilit field
storm spindle
#

So c can’t be 0 here

twilit field
#

Let me try now :

#

Let gcd(a,b)=d

#

$d \mid a \land d\mid b$ by definition
\
As proven earlier $ca \mid k \land cb \mid k$
\
It also follows that $ca \mid ck \land cb \mid ck$.
\
\
It thus follows that $gcd(ca,cb) \mid cgcd(a,b) \implies gcd(ca,cb) \geq cgcd(a,b)$

grand pondBOT
#

A dense set

twilit field
#

We now attempt to prove $cgcd(a,b)\mid cgcd(ca,cb)$

grand pondBOT
#

A dense set

midnight plankBOT
#

@twilit field Has your question been resolved?

twilit field
#

I'll correct it after dinner

twilit field
grand pondBOT
#

A dense set

twilit field
#

Let $gcd(ca,cb)=k$ . By definition $k \mid ca \land k \mid cb$. We let $gcd(a,b)= l$. We wish to show that $ cl \mid k$

visual tiger
#

not sure this is what you want

#

because proving what you wrote would imply gcd(ca,cb) | gcd(a,b)

grand pondBOT
#

A dense set

twilit field
#

We prove this via contradiction

#

We assume that $ k \nmid cl$

#

so $k = clq_1 + r; 0<r<cl$

grand pondBOT
#

A dense set

sinful trout
#

this is still going?

twilit field
#

I was eating dinner until a while ago

#

We start by dividing across by $c$ . This gives us $\frac{k}{c} = lq_1 + \frac{r}{c}$

grand pondBOT
#

A dense set

twilit field
#

We know that $c \mid k$. It thus follows that $r$ is a multiple of $c$ or is 0

grand pondBOT
#

A dense set

twilit field
#

Okay, now what

#

<@&286206848099549185>

#

Let $gcd(ca,cb)=k$ . By definition $k \mid ca \land k \mid cb$. We let $gcd(a,b)= l$. We wish to show that $ cl \mid k$

grand pondBOT
#

A dense set

twilit field
#

From this we can conclude that $ l\ mid a \land l\mod b$

#

so $ca=kq_1; cb = kq_2$
\
We also know that $a=lq_3; b=lq_4$

grand pondBOT
#

A dense set

twilit field
#

okay

#

thanks

#

so just to be sure we let d be the gcd of (a,b)

#

so $d \mid a\land d \mid b$ . We then let $ D \mid ca$ and $D \mid cb$ . It also follows that $cd \mid ca \land cd \mid cb$

grand pondBOT
#

A dense set

twilit field
grand pondBOT
#

A dense set

twilit field
#

It thus follows that $dk_1=Dk_3$; $dk_2=Dk_4$

grand pondBOT
#

A dense set

twilit field
#

that doesn't help me much

#

We wish to prove that $. c gcd(a,b) \mid gcd(ca,cb)$

grand pondBOT
#

A dense set

twilit field
#

Let's assume that $cgcd(a,b) \nmid gcd(ca,cb)$

grand pondBOT
#

A dense set

twilit field
#

$cl \nmid d$

grand pondBOT
#

A dense set

twilit field
#

so $d = clq_1+r$

grand pondBOT
#

A dense set

twilit field
#

dividing across by $c$, we find thet $r=0$ or $r$ is a multiple of $c$

grand pondBOT
#

A dense set

twilit field
#

.close

midnight plankBOT
#
Channel closed

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twilit field
#

let $\alpha >1$. Show if $|f(x) \leq |x|^{\alpha}$, prove $f$ is differentiable at $0$

grand pondBOT
#

A dense set

twilit field
#

So here, I'll have to prove continuity first, do I have to use $\varepsilon-\delta$

grand pondBOT
#

A dense set

zealous schooner
#

well if you want to be precise then yes

#

how else would you prove continuity?

twilit field
#

LHL=RHL = F(x)

fallow scarab
#

Why do you need to prove continuity first?

twilit field
#

Only then can I even consider it being differentiable

fallow scarab
#

I don't see why

twilit field
grand pondBOT
#

A dense set

twilit field
#

like I know that $|f(0)| \leq 0$

#

oh

grand pondBOT
#

A dense set

twilit field
#

that gives me $f(0)=0$

grand pondBOT
#

A dense set

merry pewter
#

Just apply the definition of differentiability

twilit field
#

Yeah

#

realised now

#

We have $|f(0+h)-f(0)| \leq |h|^\alpha$
\
We thus have $\abs{\frac{f(0+h)-0}{h}} \leq |h|^{\alpha -1}$

grand pondBOT
#

A dense set

twilit field
#

We now take the limit of both sides as h tends to $0$

grand pondBOT
#

A dense set

twilit field
#

$\lim_{h \to 0} \abs{\frac{f(0+h)-0}{h}} \leq \lim_{h \to 0} |h|^{\alpha -1}$

grand pondBOT
#

A dense set

twilit field
#

It's apparent from this that the lhe derivative is $0$, and that the function is differentiable

grand pondBOT
#

A dense set

twilit field
#

Is this enough

midnight plankBOT
#

@twilit field Has your question been resolved?

twilit field
#

@helpe

#

<@&286206848099549185>

#

.close

midnight plankBOT
#
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Use .reopen if this was a mistake.

midnight plankBOT
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last slate
#

mfs i need help

midnight plankBOT
#

Please don't occupy multiple help channels.

last slate
#

Maple Grove High School is designing an L-shaped walking path for their campus. The longer straight section of the path is 4y+7 meters, and the shorter section is 3y−2 meters, where y represents a variable length. The width of the path is consistent at y+1 meters throughout. Write a simplified polynomial expression to represent the perimeter of this L-shaped walking path.

#

.close

midnight plankBOT
#
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midnight plankBOT
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long dagger
#

A sphere of solid material of specific gravity 8 has a concentric spherical cavity and just sinks in water. What must be the ratio of radius of cavity to that of outer radius of the sphere?

long dagger
#

I solved it just now

#

No worries

#

.close

midnight plankBOT
#
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last slate
#

ok

midnight plankBOT
#
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marsh veldt
#

What did I do wrong here to get the incorrect solution pi/2 + npi instead of pi/2 + 2npi (more specifically, why can't n be an odd integer in npi)?
Given: cscx + cotx = 1
1/sinx + cosx/sinx = 1
cosx + 1 = sinx
cos^2 x + 2cosx + 1 = sin^2 x
2cos^2 x + 2cosx = 0
2cosx(cosx + 1) = 0
x = pi/2 + npi, pi + 2npi

blissful talon
#

When you square both sides, you introduce new answers to the question. That means that you have to check the answers you get.

#

For example, say I have (x-1)=4

#

(x-1)^2 = 16

#

When I factor and solve, I get x=5 or x=-3

#

but -3 was not an answer to the original question

marsh veldt
fallow scarab
#

where even is your problem

blissful talon
blissful talon
fallow scarab
#

they say that's a given?

marsh veldt
#

That’s the problem

fallow scarab
#

that's an equation. what are you supposed to calculate

marsh veldt
#

x

blissful talon
#

I know it's not the best way to pose a problem, but you can tell from context

marsh veldt
#

yea mb

blissful talon
#

unless you're not actually asking and you're just trying to get GoldenTrash to format better

marsh veldt
#

I just listed my steps afterwards

dusk owl
#

By comparing with Cos theta = Cos Alfa
We get, theta = 2nπ + alfa

marsh veldt
dusk owl
#

Check ur last step

dusk owl
marsh veldt
#

what is alfa in this case

dusk owl
marsh veldt
#

but 0 comes every pi interval

dusk owl
#

What's ur doubt now

marsh veldt
#

I don’t understand why to compare cos theta with cos alfa

dusk owl
#

Replace theta with x

dusk owl
#

R u from India?

marsh veldt
#

no united states

dusk owl
#

Ohh so ig ur textbook can have different formula

marsh veldt
dusk owl
#

Wait

#

Do u have formula sheet

marsh veldt
#

no

dusk owl
#

Any textbook?

marsh veldt
#

no

dusk owl
#

By this theorem

dusk owl
marsh veldt
#

but why isn’t + npi the solution

#

because 0 also comes twice within 2pi

dusk owl
#

Yess

dusk owl
# dusk owl

U can check last second line where we took 2 common

#

@marsh veldt Got the reason?

marsh veldt
#

why doesnt pi/2 + npi work for the equation if the solution for 2cosx = 0 is pi/2 + npi though

dusk owl
#

Is π/2 + nπ correct answer

marsh veldt
#

no

dusk owl
#

Wait

#

Actually for this solution I applied wrong formula 😅

marsh veldt
#

no worries, but the answer is pi/2 + 2npi
I was confused on how to obtain that answer

dusk owl
#

Wait I am sending u the solution

#

In my country, it's completely based on formula

#

Please replace theta with x cuz we use theta mostly so it's in my habit 😅

marsh veldt
#

but the correct answer is pi/2 + 2npi

dusk owl
#

U will get two answers

#

2nπ + π & nπ + π/2

dusk owl
marsh veldt
#

yes

#

you can graph it

dusk owl
#

Ig now I am unable to solve it

dusk owl
marsh veldt
#

n = odd numbers does not work

dusk owl
marsh veldt
#

that's what I was asking for

#

why pi/2 + npi wasn't a solution

dusk owl
#

Ig I'll take time to understand this 😅

marsh veldt
#

ok ty for your help

dusk owl
#

Sorry sorry

#

I am unable to help

#

Please reopen ur question

#

But thanks a lot u helped me clearing my concept ✨

marsh veldt
#

yea np ig

midnight plankBOT
#

@marsh veldt Has your question been resolved?

midnight plankBOT
#

@marsh veldt Has your question been resolved?

marsh veldt
#

.close

midnight plankBOT
#
Channel closed

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midnight plankBOT
#
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mental bone
midnight plankBOT
mental bone
#

How do I find where the function is increasing and decreasing?

#

I found the derivative:

dawn dagger
#

you can also use |x| and think about how the transformations affected f(x)

mental bone
dawn dagger
#

nope

mental bone
#

Hmm... how would I determine them using the derivative tho

dawn dagger
#

sure

#

you would have to see for increasing f' > 0 and for decreasing f' < 0

mental bone
#

Yeah I know but I'm just having trouble

#

Because how I do it is i find the critical point then determine how the function behaves using nearby points

runic hamlet
#

its so much easier to do the derivative by cases instead of this inconvenient thing

runic hamlet
#

just do cases depending on whether the inside of the absolute value is >=0 or not

mental bone
#

ok

grand pondBOT
#

bacc (unhelpful)

mental bone
#

Ahh I see

runic hamlet
#

also your derivative isnt correct

mental bone
#

okay let me try

mental bone
mental bone
#

or just -2?

floral apex
#

you need to apply the piecewise defn of absolute value

#

|y| = y if y>= 0

mental bone
#

ohhh i see

floral apex
#

|y| = -y if y < 0

dawn dagger
#

you neglect the denominator since at x = 3 is not differentiable anyway so you really solve -2(x-3) >= 0 and -2(x-3) < 0

midnight plankBOT
#

@mental bone Has your question been resolved?

#
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neat canyon
midnight plankBOT
neat canyon
#

how do i prove this identity

#

should i use transformation to product

violet lion
grand pondBOT
#

timuko

neat canyon
#

for the rhs?

violet lion
neat canyon
#

is it easier from there

violet lion
#

Maybe try using complex numbers

neat canyon
#

i have not learnt them

violet lion
#

$\cos(3x)=\cos(x+2x)=\cos(x)\cos(2x) - \sin(x)\sin(2x) = \cos x(2\cos^2 x - 1) - 2\sin^2 x \cos x = 2\cos^3 x - \cos x - 2\cos x(1 - \cos^2 x) = 2\cos^3 x - \cos x - 2\cos x + 2\cos^3 x = 4\cos^3 x - 3\cos x$

grand pondBOT
#

timuko

last slate
#

You could do this

#

Or

#

You could use the property
CosA +CosB = 1/2 Cos(A+B/2) Cos(A-B/2)

#

A being 3x and B as 5x

violet lion
neat canyon
#

but its a difference

#

ohh

#

i can take out the negative sign

last slate
#

You could then use Cos(2x) = 2cos^2(x) -1

last slate
last slate
neat canyon
#

do they cancel out with the 2

violet lion
grand pondBOT
#

timuko

neat canyon
#

oh ye

#

cos(x) - cos(4x)*cos(x)

#

cos(x) * (1-cos(4x))

violet lion
grand pondBOT
#

timuko

violet lion
#

Like $\sin 2x = \pm \sqrt{\frac{1-\cos 4x}{2}}$

grand pondBOT
#

timuko

neat canyon
#

yea i see it

violet lion
#

Here is a cheat-sheet:

neat canyon
#

i know them

neat canyon
last slate
#

First your x would be 2x,if that made any sense XD

neat canyon
#

2cos^2(2x) - 1

last slate
neat canyon
#

like

#

cosx*(1 - 2cos^(2x) - 1)

#

or cosx * (1 - 2cos^2(2x) + 1)

last slate
#

What do you thin

#

Thunkz

#

Think*

#

Lol

neat canyon
#

honestly

neat canyon
last slate
#

You are right

neat canyon
#

ok i have

#

cosx*(2-2cos^2(2x)

last slate
#

Huh

#

Yeah yeah

neat canyon
#

1+1 right?

last slate
#

Good

neat canyon
#

so

last slate
#

Go on

neat canyon
#

do i use

#

cos(2x) = cos^2(x) - sen^2(x)

#

or ig i could take the 2 out

#

2(1-cos^2(2x)

#

and change that to sin^2(2x)

last slate
#

Ah!

#

Apologies

last slate
#

Using cos2x equals 1- 2sin^2 x eliminates the 1

neat canyon
#

oh yeah

#

but we get to the same thing anyways

#

or not

#

i think not

#

ok

#

cos(x) *(1 - 1 + 2sin^(2x))

#

oh we do

#

cos(x)*(2sin^2(2x)

last slate
neat canyon
#

cos(x)*(2.2sin^2(x)cos^2(x)

last slate
#

Got a number wrong

neat canyon
#

huh

#

where

#

sin(2x) = 2cosx.senx

#

so isnt sin^2(2x) = 4sen^2(x).cos^2(x)

last slate
#

It is

#

Not

#

won't the 2 also get squared?

neat canyon
#

ohh

#

lmao

#

ye mb

#

sin^2(2x) = 4sen^2(x).cos^2(x)

last slate
#

You got it right nos

#

Now

neat canyon
#

ok

#

we already proved it

#

2.4 = 8

#

cosx(8sen^2(x)cos^2(x))

#

and that does it

last slate
#

Yep

neat canyon
#

thanks

#

.clos

#

.close

midnight plankBOT
#
Channel closed

Closed by @neat canyon

Use .reopen if this was a mistake.

midnight plankBOT
#
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vital vault
midnight plankBOT
vital vault
#

This is the one issue I have is finding the asymptotes, I tried y = 900, y = 0 and was wrong? not sure what I am missing

hearty rune
#

you have written the equation of a vertical line

#

what happens as t tends to infinity

#

specifically to the e^(-0.1692t)

#

oh actually

#

i see, did you actually write 'y'?

#

try p

vital vault
#

Originally I did because I was listing the asymptots at y = 900

#

I did t = kinda as just a shot in the dark

hearty rune
#

horizontal lines on that graph will be of the form p(t)=a

#

rather than y

vital vault
#

ohh

#

so would it be p(t) = and then where the asymtots cordinate is?

#

like p(t) = 900 yeah?

hearty rune
#

you can skip the t but yeah

vital vault
#

ohh ok ok

hearty rune
#

p=900, p=0 should be okay

#

wait no

#

the 0 is fine, the 900 not

#

sorry ignore that, got confused

#

youre good

vital vault
#

So my original listing of 0 and 900 was right I was just missing p=?

hearty rune
#

yup

vital vault
#

Ohhhh ok ok

#

thanks

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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meager plover
#

hi can someone explain how for problem c, it’s 42 seconds? i dont get it 🥲🥲🥲

sleek cloud
#

Why did you label the second peak 42

midnight plankBOT
#

@meager plover Has your question been resolved?

meager plover
sleek cloud
#

How?

meager plover
#

for c or just on my graph

sleek cloud
#

Your graph

meager plover
#

the max distance is 25 yds, and michael reached 25 yds in 21 seconds

since the graph is in a cycle, the period is 21 seconds. so he completed 25 yds for the second time in the timeframe of 0-42 seconds

sleek cloud
#

Isn't the second time when he returns back?

#

When the distance is back to 0?

meager plover
meager plover
sleek cloud
#

The 42 should be when the distance returns to 0 first time

#

The period can also be from 0 to 0

#

Which is 42

meager plover
#

after another 21 seconds, he reached the max distand again

#

21+21=42

sleek cloud
#

Max distance?

meager plover
#

pool is 25 yds long

sleek cloud
#

Yeah it takes 21 seconds to swim 25 yards

#

And then 21 seconds again to return from the other side to starting point

meager plover
#

Hm

#

because the answer key said point D is 84 seconds

#

Wait

#

Ohhhhhhhhhhh

#

no youre right

#

i get it now

#

sorry i thought for whatever reason, 42+21=84 😅😅😅

#

Wait but i dont get why it takes 42 seconds to get from point A to point C

sleek cloud
#

Because that's a period

meager plover
#

Oh so the period is actualy 42 seconds

#

😭😭😭

#

Ok my brain just doesn’t wanna function simple math

#

ok ty

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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grand canopy
#

help me

midnight plankBOT
grand canopy
#

first part is just solve for roots and factorise over the real field noting cos4π/5 = -cosπ/5
how do i find cosπ/5 and cos2π/5

midnight plankBOT
#
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
grand canopy
#

i tried SOR and POR of the quadratics but that doen't really help me

small jasper
#

Sum of roots should work tbh

#

What did you do with it

grand canopy
#

with the 2nd quadratic

#

cis2π/5 + cis(-2π/5) = 2cos2π/5

#

but that's just a true statement cuz LHS is 2Re(z)

#

similar with POR

small jasper
#

Consider the sum of the roots from all three factors. What must this sum be equal to (||consider the left hand side||)?

grand canopy
#

ohh

#

1 + cis(2π/5) + cis(-2π/5) + cis(4π/5) + cis(-4π/5) = 0

#

1 + 2cos(2π/5) + 2cos(4π/5) = 0

#

cos2π/5 - cosπ/5 = -1/2

#

then do i use POR ?

small jasper
#

nah

#

||double angle||

grand canopy
#

oh so i do cos(2π/5) = 2cos^2(π/5) - 1

#

sub into the other equation and get a quadratic

#

solve then choose whichever solution is right?

#

ok i got it now

#

THANK you

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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leaden matrix
midnight plankBOT
leaden matrix
#

could someone explain how to go from that top right equation to the bottom one?

sharp coral
#

y = (y - 3) + 3

#

similarly x = (x - 1) + 1

lavish venture
#

$\frac{y-3}{y-3} + \frac{3}{y-3}$

grand pondBOT
leaden matrix
#

ty

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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pseudo moat
#

The perimeter of a rectangle is 80dm. The width is 1 more than 1/2 of the length. Find the length and the width of the rectangle.

pseudo moat
#

do I use substitution

lavish venture
#

what’s the formula for perimeter of a rectangle

pseudo moat
#

P = 2(L + W)

stable dawn
#

half of length

lavish venture
weary nest
#

Yeah I just realised lmao

#

Substitute W=(L/2)+1

pseudo moat
#

how

lavish venture
#

half the length plus 1

#

L/2 is half the length

#

then add 1

weary nest
pseudo moat
#

L/2?

weary nest
lavish venture
#

yes L divided by 2

weary nest
#

Length divided by 2

lavish venture
#

which is half the length

pseudo moat
#

can you show it, i don't understand in terms of text

weary nest
#

Ok what do you not understand

pseudo moat
#

all of it, can you start again, im lost

weary nest
#

Ok sure

#

Let me draw it out for you

#

Gimme some time

stable dawn
#

But length is a variable here which we have to find so we denote it with L.

weary nest
#

Does that clear it up

pseudo moat
#

where did 3L + 2 = 80 came from

weary nest
#

Because we have already established that W is equal to L/2 +1

#

Then because you multiple everything by 2

#

You get this

#

Then you add them together

pseudo moat
#

but it's only 2L

weary nest
#

Do you know how to expand brackets?

#

Look at the very top line in the photo

#

Everything in between the brackets have to be multiplied by the number directly next to the brackets

#

So multiply everything by 2

pseudo moat
#

yes

weary nest
#

So what are you not understanding

#

Which part

pseudo moat
# weary nest

just got a lil confused with this, but I understand it

weary nest
#

Ah ok

#

So you’re all good?

pseudo moat
#

so what's the length and width

midnight plankBOT
#

@pseudo moat Has your question been resolved?

pseudo moat
#

is that correct

midnight plankBOT
#

@pseudo moat Has your question been resolved?

#
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midnight plankBOT
#
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nova pike
#

hello, i dont know how to approach this following problem: in graph theory, let us describe a simple graph of n vertices and m edges assigned an integer value from 0 onwards. in each operation, when you chose a pair of connected vertices, one minuses 1 from one vertice's value and adds 1 to the other. call the task winnable if it is impossible after applying any number of iterations no two linked vertices are both 0, and let the smallest sum across all the n vertices be k. find all possible values of k, given m and n

nova pike
midnight plankBOT
#

@nova pike Has your question been resolved?

nova pike
merry pewter
hexed pilot
merry pewter
#

well it seems like if the initial sum is fixed, then the sum is always the same since subing 1 and adding 1 keeps the sum constant

nova pike
nova pike
merry pewter
#

i think he means a search with a computer

hexed pilot
#

yes

#

I can write a program in Java that can help you solve this

#

but the problem is I don't understand the point of this problem?

#

What is it trying to achieve ultimately??

merry pewter
#

also fyi, a forest is a set of disjoint trees, which i assume is not what you are talking about

hexed pilot
#

yes, and a tree can also be classified as a type of graph

merry pewter
nova pike
merry pewter
nova pike
merry pewter
nova pike
merry pewter
#

not necessarily a tree

#

or a forest

#

simple means that there is at most one edge between vertices and each edge is between exactly two vertices like you said

nova pike
merry pewter
#

then it's a bit tricky because for some values of m, there are no winnable graphs

merry pewter
#

namely if m = n(n-1)/2, so that the graph is a complete graph

#

then, you can always make two of the vertices 0

#

im not sure if there will be a closed form

nova pike
#

What happens if we fix a m and n? Then would we be able to compute all possible values of k easily?

grizzled pivot
#

Is the following graph winnable? (0)—(1)—(0)

merry pewter
#

wait but now it seems like any graph with three vertices that are connected in a row is unwinnable

merry pewter
nova pike
merry pewter
#

ok, then it seems like there are actually few values of m so that a graph with n vertices is winnable

nova pike
grizzled pivot
#

yeye you got it

merry pewter
#

so i think when m < n/2, there are n(n-1) possible values of k, and 0 otherwise

merry pewter
#

because when m > n/2, then there three vertices that are connected

#

which means that the graph is unwinnable

nova pike
#

so if there was a graph with 100 vertices and 1000 edges, then there does not exist such graph?

merry pewter
#

and therefore, if the numbers are x-y-z, then you can make (0)-(0)-(x+y+z)

#

actually a funny edge case is when m = 0, then you can have n(n-1)+1 values of k

nova pike
merry pewter
merry pewter
#

but if there is at least one edge, then the sum has to be at least 1

nova pike
#

Oh, I think I made also a terrible mistake in what I was trying to say which makes the problem much more complicated. The person that is making each iteration wants there to be a 0-0 but the vertices move in a way that always try to avoid this

merry pewter
#

how

#

do you mean the vertices are arranged so that the graph is unwinnable?

nova pike
#

Im so sorry, I really wanted to convert the original problem into a graph theory one

merry pewter
#

so for m>=2, the only value of k is 0

#

and when m=1 there are n(n-1) values of k

#

and when m=0 there are n(n-1)+1 values of k

merry pewter
nova pike
# nova pike

I thought replacing 100 with n and 1000 with m would help solve the problem in general

merry pewter
#

oh i see, so merlin gets to chose the edge, but not the direction in which the wise men move

#

this is quite different to the earlier statement

nova pike
nova pike
merry pewter
nova pike
merry pewter
#

hmm, then it is a tricky problem, let me think

nova pike
merry pewter
#

well im very stuck, it seems like it highly depends on the structure of the castle

#

one idea is to alternate the parity of every room

#

since then, the parity of each adjacent room will swap, hence not both can be 0

#

but this is not always possible, depending on castle layout

#

you would need a bipartite coloring

merry pewter
#

wait but then the parity will be the same on the other side

#

so this doesn't work

nova pike
merry pewter
#

ok, it is giving me a lot of trouble, i would suggest pinging helpers again, or asking in #discrete-math , or asking again when more people are awake

nova pike
nova pike
merry pewter
merry pewter
#

and then saying how you reformulated the problem

midnight plankBOT
#

@nova pike Has your question been resolved?

nova pike
# nova pike

<@&286206848099549185> here is the problem. instead of 100 rooms, i tried breaking it down into 2, 3 etc. but from >3, it becomes hard finding the best and minimal possible construction

fervent ember
#

i have two questions:

  1. whats the meaning of "every minute" as there is no other time relevant information in it? would it be the same if its just "every thirty seconds" or "every hour"?
  2. if merlin has choosen a corridor and a wise man psssed along it, would it be a simple strategy if the wise man will go back?
nova pike
fervent ember
#

does this mean the wise men can only move after a choice of merlin?

nova pike
fervent ember
#

ok, then i do understand nothing. whats the meaning of "the wise men needs to scatter across the rooms in a manner they wish"?

#

if only one man can move and only in the corridor which is defined by merlin i cant see a "a manner they wish"?

nova pike
nova pike
nova pike
#

<@&286206848099549185> if someone could help with this problem (which looks like theres some graph theory in disguise), that would be much appreciated

ocean dune
#

Does Merlin win if there's no wise man in a room but there's one in the other

nova pike