#help-10

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obtuse pebbleBOT
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fathom flicker
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I need help following along with this proof about sequence convergence. $\newline$ If ${x_n}$ is a sequence and it converges to x and to y, then $x=y$. I'll start typing out the proof below

warm shaleBOT
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AustinU

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AustinU

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AustinU

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AustinU

fathom flicker
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this following step is the step that I am lost at, I don't see where it comes from

warm shaleBOT
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AustinU

fathom flicker
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Any help understanding where this final equality comes from would be appreciated. Please tag me if you respond.

sonic anchor
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they added 0

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$-x_{M_1+M_2}$ and $x_{M_1+M_2}$

warm shaleBOT
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Køter

sonic anchor
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and im assuming the the real implication then is that that is < epsilon/2+epsilon/2=epsilon

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showing x and y are epsilon close for some m1 and m2

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@fathom flicker

fathom flicker
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because that's 0

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gotcha

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I was just wondering where those pieces came from lol

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yeah, that is what happens next in the proof

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triangle inequality

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and then we show that |x-y| < epsilon for all positive epsilon

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so x=y

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Ty Koter!

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obtuse pebbleBOT
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tall forge
obtuse pebbleBOT
tall forge
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Can some one help with question 1

violet sentinel
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!status

obtuse pebbleBOT
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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'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
tall forge
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1

sonic anchor
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find out how big a fraction of the profit comes from the jumping castle

obtuse pebbleBOT
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@tall forge Has your question been resolved?

obtuse pebbleBOT
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obtuse pebbleBOT
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shy agate
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how to prove with part one of FTC

obtuse pebbleBOT
sage geode
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How to prove what?

shy agate
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g'(x)

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find g'(x) i mean

sage geode
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Alright, what do you mean by part one of FTC btw?

shy agate
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part one of fundamental therom of calculus

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the easiest one

sage geode
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According to FTC, y = F(1) - F(1 - 3x) where F'(u) = u^3/(1 + u^2)

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So y' = -F'(1 - 3x) * (-3) or simply 3(1 - 3x)^3/(1 + (1 - 3x)^2)

shy agate
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ok so

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basically factoring the negative flip the upper bond and the lower bond of the intergals upside down?

sage geode
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Yes

shy agate
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that applies to every intergrals?

sage geode
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Yes

shy agate
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thx

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obtuse pebbleBOT
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timid silo
obtuse pebbleBOT
timid silo
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!status

obtuse pebbleBOT
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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'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
timid silo
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4

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Is the range [0,1)?

sage geode
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Yeah

timid silo
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And I can rigorously write that like :
f = {(x, f(x)): x is an element of R}. The range is the set of all the values that f(x) can assume given real x. so, x^2/ (1+x^2) = f(x).
So when x= 0, f(x) = 0.
As x approaches neg infinity, f(x) approaches 1. Similarly when x approaches positive infinity, f(x) approaches 1.
Therefore the range must be [0,1)

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I am trying to learn to be more rigorous

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Is there something I should change here to do so?

sage geode
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That is not enough

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You just said f(0) = 0 and f(x) -> 1 at infinity

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Which does not mean the range is [0, 1)

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Instead you just need to prove the inequality 0 <= x^2/(1 + x^2) < 1 for all real x

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0 <= x^2/(1 + x^2) is always true because x^2 and 1 + x^2 are both nonnegative numbers

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And x^2/(1 + x^2) < 1 is true because x^2 < 1 + x^2

timid silo
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I understand

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But that is a verification that that is the range

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How do I frame my answer

timid silo
undone ferry
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I have also been doing this ques since 20 minutes, though it is intuitive that the answer is [0, 1) I am trying to prove this

timid silo
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i think once we get an intuitive idea, we can just show that its that like Lonely Bean said

undone ferry
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That doesn't clear concept tbh

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I have a solution I am not sure if it works

timid silo
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Mind sending it in

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I was thinking that we could also do this

undone ferry
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Ya sure 2 mins

timid silo
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$\frac{x^2}{x^2 + 1} = \frac{(x^2 + 1) - 1}{x^2 + 1} = \frac{x^2+1}{x^2 +1} - \frac{1}{x^2 + 1}$

warm shaleBOT
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Matchstick

timid silo
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that would be $1 - \frac{1}{x^2 + 1}$

warm shaleBOT
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Matchstick

undone ferry
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Highly incorrect imo and the range is not even coming correct but i think this is how it would be approached

timid silo
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but that brings us to the same spot as before, we still have to go the same route

undone ferry
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sorry i am on PC so can't use camera for photos

undone ferry
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I could do it with Sign Scheme method but x^2 will then nvr be -1

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bcz root of -1 doesn't exist

timid silo
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you wrote the incorrect range in the last step

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wait

undone ferry
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I told you range is not even coming correct

timid silo
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we could let x^2 /(x^2 +1) equal to 0. find x in that case

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and then we could use that x^2 > 0

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that will do

undone ferry
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I have an idea

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give me a min

timid silo
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we'll have two cases x^2 = 0 and x^2 > 0

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sure

undone ferry
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Yes

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u r right

timid silo
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bro are you solving ncert?

undone ferry
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Maybe we could use above x^2+1/x^2 >= 0
and put x belongs to (-infinity, infinity)
Basically to takee very large numbers on both sides and then determine the range

timid silo
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we could but i was told that wasnt enough

undone ferry
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for JEE

timid silo
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ahh

undone ferry
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Why r easiest problems most difficult to prove

timid silo
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i dont know angerysad

undone ferry
timid silo
undone ferry
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This would have been very easy if x^2 could be
-1

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but that is not possible

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Maybe we can put f(x) in a variable

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I'll try this approach

timid silo
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put in what?

undone ferry
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Got the answer

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let's go

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Finally

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I'll share it, one second

timid silo
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alr

undone ferry
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Basically if you put anything including 1 or above then the solution will be negative but inquality says solution can only be 0 or greater than 0

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This one is incomplete actually let me complete it

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If you put y < 0 then also the solution will be -ve which goes against >= 0

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1 and 0 are the roots of equations y and 1-y

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called critical points

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and we do not include 1 bcz the 1/0 is undefined

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@timid silo Did u understand?

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1 hour wasted, phew

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i feel worthless

timid silo
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how did you find the critical points?

undone ferry
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1-y = 0
Y = 1

y = 0

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Critical points r points where these variables will change signs

timid silo
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ahh

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wait leme digest this

undone ferry
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If you put -60 as y for ex
-60 / (1-(-60) = -60/61 which is ngative and smaller than zero soc an't be the solution

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There is a method called Sign scheme or Wavy curve method which is not in NCERT syllabus but is very helpful

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where we put signs on the number line

timid silo
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ahh okay

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i think i understand

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thank you so much:)

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obtuse pebbleBOT
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lavish sequoia
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Ok if an airplane covers 7007 miles in 98 upon 35 hours how long did it travel in 1 hour

lavish sequoia
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ok i simplified it to if a airplane cover 1001 miles in 14 upon 5 hours

rich plume
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Let the plane cover x distance in one hour

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So if in 1 hour it covers x distance, what distance does it cover in 2 hours?

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@lavish sequoia

lavish sequoia
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x times 2

rich plume
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Yes

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Or 2x

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So what distance does it cover in 98/35 hours?

lavish sequoia
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98x?

rich plume
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No

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Notice how many hours

lavish sequoia
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35x?

rich plume
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No

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Let's see another example

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Okay what distance is covered in 0.5 hours

lavish sequoia
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x upon 2

rich plume
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Can we write 0.5 as 1/2?

rich plume
lavish sequoia
rich plume
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So in 1/2 hours the distance covered is (1/2)x

lavish sequoia
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yes

rich plume
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So can you now answer the distance covered in 98/35 hours?

lavish sequoia
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im sorry i dont get it 😭

rich plume
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Okay can you write 98/35 as a decimal?

lavish sequoia
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2.8 right

rich plume
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Yes

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So the plane covers x distance in 1 hour
2x distance in 2 hours
So what is distance covered in 2.8 hours?

lavish sequoia
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2.8x?

rich plume
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Yess

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But we are given the plane covers 7007 miles in 2.8 hours

lavish sequoia
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yes

rich plume
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So both the quantities 2.8x and 7007 are equal

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2.8x=7007

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Now you can solve for x

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Which is required ans

lavish sequoia
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oh thank you

rich plume
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Welcome

lavish sequoia
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obtuse pebbleBOT
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light flume
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I came across an interesting question that asks to express sqrt 2 as an approximation in fraction

light flume
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or using the words of the question

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"Deduce sqrt2 as 1/(2+1/(2+1/2.....)))

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i understand that it is irrational so thereby cannot be expressed correctly as a fraction (at least not in a form we can count)

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but how would u go about proving this

rich plume
light flume
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@rich plume here

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scope of my knowledge is yr11 highschool

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im not too sure how different australian curriculum is to elsewhere

rich plume
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The RHS is an infinite repeating series below numerator

light flume
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yep i recognise that

rich plume
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Assume this quantity to be x

light flume
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just before u proceed more into the question

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generally when it says deduce, u arent really meant to use the RHS

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and supposed to generate it from purely elsewhere

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if that makes sense

runic void
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I see this as recursively replacing \sqrt(2)

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Hopefully this will make sense

night moth
light flume
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ah ok

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dang

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thats quite neat way

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so thereby every irrational number is expressable this way?

runic void
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isn’t this ramanujan continued fractions?

night moth
light flume
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right

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so all algebraic irrational numbers are expressable in recursive

night moth
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yep

light flume
# runic void isn’t this ramanujan continued fractions?

The Rogers–Ramanujan continued fraction is a continued fraction discovered by Rogers (1894) and independently by Srinivasa Ramanujan, and closely related to the Rogers–Ramanujan identities. It can be evaluated explicitly for a broad class of values of its argument.

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god dang this cant be it man

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im screwed if this shows up intest

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T=T

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i suppose its still doable without full understanding of the theorem above

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thx for the help

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.close

obtuse pebbleBOT
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edgy needle
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Hi how do i do qb ii

obtuse pebbleBOT
edgy needle
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ohh wait

rich plume
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use the exponent rule a^n/a^m=a^(n-m)

edgy needle
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But before that

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Do i add a^5/2 to a^1/2

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So its 6/2

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OHHHHH

rich plume
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and a^n*a^m=a^(m+n)

edgy needle
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CALL ME A GENIUSSSSSS

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stop

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can u check this question

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part b

rich plume
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all correct

edgy needle
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ah ok and this one

rich plume
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correct

obtuse pebbleBOT
#

@edgy needle Has your question been resolved?

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vestal island
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Hey everyone, can someone help me on the topic of multiple regression analysis? I am asked to assess the reliability of my multiple regression model, which I am unsure as to which models/test could best justify this. If someone could help, I could additionally provide the data and context too. Thanks

vestal island
obtuse pebbleBOT
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@vestal island Has your question been resolved?

vestal island
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<@&286206848099549185> catthumbsup

tame narwhal
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how are they defining "reliable"

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and yes, some more context and showing the data would be helpful

vestal island
# tame narwhal how are they defining "reliable"

this is also what im confused about. I'm guessing it's just whether the regression is valid (not violating any regression assumptions) and is statistically significant, but I'm not entirely sure.

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Here is the output of the multiple regression model. Basically we are analysing whether certain variables such as field goal %, 3 point %, free throw %, turnovers, and the introduction of a new ball (dummy variable) impact the scores made by a basketball team in a season.

tame narwhal
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"statistical significance" should not have anything to do w/ "reliability"

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has your textbook and/or teacher defined "reliable" in this context

vestal island
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no they havent unfortunately

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would it be simply whether the model has pitfalls or not?

tame narwhal
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so they say "reliable in terms of predicting the scores made by the team". does that mean they want you to predict total score per game, using the model? is there more to the question?

tame narwhal
vestal island
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so the overarching question is they gave us a set of data and instructed us to create a multiple regression model with Y variable as scores made by the team, and independent X variables as the ones i mentioned above. Then, they're asking us whether this regression model is reliable in terms of predicting the scores made by the team over an entire season (which is what the data they provided us is)

vestal island
tame narwhal
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so I guess they might be asking about the residuals, perhaps. y - yhat

vestal island
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yea that was one of my initial thoughts. I was thinking residual analysis, f-test, t-tests, and/or something with r-squared?

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here's the residual plot.

tame narwhal
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those look fine IMO

vestal island
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yep, i also think that

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what do you think about using an f-test?

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does that indicate anything about reliability or is that just significance

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or arethose two terms interchangable

tame narwhal
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I don't know what reliable means TBH. it should be defined by the book or teacher

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what are TOV and NEWB?

vestal island
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TOV stands for turnovers, and NEWB is the dummy variable i created which is the introduction of a new ball design. So the dummy variable assigns =1 to games played **before **the new ball, and =0 is games played **after **the new ball.

tame narwhal
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ok. well anyway, I don't know how to answer it if they don't define "reliable", but given the residuals look reasonable I would say "yes"

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you could possibly use the F-test as justification

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since the denominator is the mean squared error

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which is low relative to the total mean square

vestal island
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yep, thats what i came to the conclusion of. Residuals look fine and f-stat significance is lower than 0.05, so its "reliable" ig.

But should I worry about the fact that 2 of the variables are statistically insignificant (i.e. p-value > 0.05) and also that multicollinearity exists across these variables?

tame narwhal
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multicollinearity could be an issue, yes. whether they are stat. significant or not doesn't

vestal island
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do you mind briefly explaining why stat significance doesn't matter?

tame narwhal
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because it is usually just an arbitrary cutoff. for an individual predictor, even if p > 0.05 that predictor still might have an important contribution towards predicting your dependent/response variable

vestal island
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right that makes sense. So it may still have an impact but cannot be distinguished from a statistical standpoint?

tame narwhal
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I don't know what "distinguished from a statistical standpoint" means

vestal island
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basically the contribution may not be captured by the p-value completely

tame narwhal
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all I'm saying is that, while the new ball design might not be "statistically significant" in terms of this model and specific dataset, it might have a real impact on total score

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statistical significance and "practical" or "real-life" significance are different things

vestal island
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yep thats what i was trying to get at, thank you

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and just one last qucik question

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the y-intercept is 19.881, does this make any sense for this regression model and its practical scenario of a basketball game?

tame narwhal
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that is the total points scored when all predictors equal 0

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so... I'm not sure how that could be possible. because that would mean FG%, 3pt%, and FT% equal 0

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and TOV=0, and NEWB=0 (which you said is after the new ball design)

vestal island
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yea so if we have NEWB=0 when interpreting the intercept, does that mean data before the new ball design is just completely cut off?

tame narwhal
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cut off?

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it just means that, if NEWB 0 is after and NEWB 1 is before, then scores are ~2.7 points higher after new ball design

vestal island
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yep but in terms of interpreting the intercept, how does that work since we only have NEWB=0?

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since we have to set the predictors to 0

tame narwhal
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it just means it's the value of y (total points) with all predictors equal to 0. it depends on the meaning of the dummy variable, which here is after new ball design was introduced

vestal island
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so when interpreting the intercept's practical meaning, we're saying that FG%, 3PT%, FT% are all equal to 0. And then the dummy variable in this scenario is set to "new ball design"

tame narwhal
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it's the same as an intercept of a straight line y = mx + b. it is nothing more than the y-value when x=0

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just in the multiple regression case, it's when all predictors/independent variables are 0, including any dummy variables

vestal island
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yeah i just dont get the dummy variable part. Because when we set that to 0, it's not like we're setting a value to 0. It has a meaning behind it (new ball design introduced) which makes it kind of weird.

tame narwhal
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it does have meaning. NEWB = 0 is for games after the new ball design was introduced

vestal island
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yeah that's what i'm saying, but just confused in regards to how that fits in when substituing all predictor values to 0 for interpreting the intercept.

because essentially we get this right;

intercept (19.881) = 0+0+0+(new ball introduced)

tame narwhal
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yeah. it definitely gets confusing with multiple predictors

vestal island
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right. So do you think its safe to conclude that the intercept doesnt really make sense from a practical/real-life relevancy viewpoint?

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since having a 0 FG, 3PT, FT is really unlikely and unrealistic

tame narwhal
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yeah, I don't see how that could be the case

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what do the data look like?

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maybe some of the rows where NEWB=0

vestal island
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here's a chunk of it when NEWB=0. Sorry i couldnt get the titles in because NEWB=0 is the second half of the data

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but yea none of it is really close to 0

tame narwhal
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oh right. so it's probably an interpolation of the regression line, and would be the value if all the other variables were 0

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which won't ever happen in real life

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so yeah, I'd say the intercept parameter is not sensible in this model

vestal island
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yea i think they were hinting at that since they one of the question asks if "the intercept makes any sense given the data you have"

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anyways, thanks so much for your help bro. Helped alot, I appreciate it

obtuse pebbleBOT
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@vestal island Has your question been resolved?

fair notch
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how did they get the f(t + 5) ?

candid yarrow
obtuse pebbleBOT
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lean kayak
#

question 8 b, i’m completely stuck, have no notes on this and have never done something like this. where do i start?

candid yarrow
lean kayak
candid yarrow
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Do you know how to find the equation of a line?

lean kayak
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y=mx + c

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??

candid yarrow
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This is the equation of any line, and now you need to find m and c for these specific lines

lean kayak
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right, but what i’m confused is that in 8 b the line is under 6

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so it’s (0,-5)and what?

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what would be the x

candid yarrow
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Next you need to find the slope, m

lean kayak
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using rise over run?

solid oxide
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Or you can use a few points and solve equations

lean kayak
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how would i do that? not sure what u mean

solid oxide
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As in you already have (0,-5)
y= mx+c
-5=0x+c
c=-5

lean kayak
#

m would be -1/2?

solid oxide
#

Where did u get that

candid yarrow
solid oxide
#

So just use a different point for example (4,-3) to find m

#

-3= 4m-5

candid yarrow
lean kayak
#

so answer should be y= 1/2 x -5?

lean kayak
solid oxide
#

Thats just another (x,y)

lean kayak
#

oh yeh yeh

solid oxide
#

But yeah you get the same result anyway

#

Im just lazy

lean kayak
#

so answer is y=1/2x -5

#

i think i got it

solid oxide
#

Yep

lean kayak
#

okay thanksss

#

.close

solid oxide
#

Np

#

its .close

lean kayak
#

.close

obtuse pebbleBOT
#
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late flare
#

for the derivative of sin(x+y)

obtuse pebbleBOT
#

Please don't occupy multiple help channels.

late flare
#

can I do derivative of sinx+siny

#

so cosx + cosy'

high lily
#

no

late flare
#

why

high lily
#

first step is already wrong

late flare
#

distributive property

paper anvil
#

What’s your issue ?

high lily
#

sin isn't a magic value being multiplied tio (x+y)

late flare
paper anvil
#

Tell fast

paper anvil
high lily
#

sine is a funnction

paper anvil
#

Done

late flare
#

so how do i find the derivative

high lily
#

distributive property doesn't apply

#

chain rule would be the most efficient

paper anvil
late flare
#

also the derivative of 2y

paper anvil
late flare
#

people say 2 dy/dx

paper anvil
#

Stop letting us complete your homework

late flare
#

is it 2 y'?

paper anvil
#

Do you know what you’re doing

#

?

late flare
#

i dont want you to complete my homework

#

i want to understand

late flare
paper anvil
#

You got photomath?

#

Download it

#

It’ll tell you everything

#

Don’t have to ask here

late flare
#

i still dont know how to find derivative of sin(x+y0

paper anvil
#

Use chatgpt then

late flare
paper anvil
#

Sin derivative is cos btw

late flare
#

chatgpt is the shittet

#

thing to use use

#

in math

paper anvil
#

Don’t have to ask here

high lily
#

<@&268886789983436800> slaysec being very intrusive, past logs/messages aren't desirable either

paper anvil
#

??

#

I’m helping the guy out

teal turret
#

by recommending chatgpt

#

Yea Aight

paper anvil
#

Chatgpt literally helped me in my math understanding for a whole sem

high lily
#

are you familiar with chain rule?

paper anvil
#

I didn’t have to ask people compared to before it came around

late flare
#

yes i am

#

f'(gx) multiply gx'

paper anvil
late flare
#

the x + y is the gx

high lily
#

(f(g(x))' = f'(g(x)) * g'(x)
can you apply that here

late flare
#

what is the derivative of y?

#

y' or 1

paper anvil
#

1

late flare
#

why

high lily
#

no

late flare
#

that what confuses me

paper anvil
#

Any variable derivative is 1

high lily
#

ignore them

paper anvil
#

?

high lily
#

they're feeding you all the wrong info

paper anvil
late flare
paper anvil
#

And differentiation ?

high lily
#

yes y' is literally the derivative of y

#

(wrt to your variable)

paper anvil
#

If y = some function of x (in other words if y is equal to an expression containing numbers and x's), then the derivative of y (with respect to x) is written dy/dx, pronounced "dee y by dee x"

late flare
#

so it should be cos(x+y) multiply 1+y'

paper anvil
#

Yes

high lily
#

cos(x+y) * (1+y')

late flare
#

i got it , thanks @high lily and @paper anvil

plucky swan
#

stop encouraging people to use photomath or chatgpt for the things they ask here slaysec

paper anvil
#

Happy to help

paper anvil
trim portal
paper anvil
paper anvil
candid yarrow
obtuse pebbleBOT
# paper anvil Cos x + 1

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.

trim portal
paper anvil
plucky swan
paper anvil
#

But I learnt differentiation and integration that way no one taught me

#

I could understand faster than watching YouTube tutorials

plucky swan
#

This is not a discussion about it's usage, we don't want this here on this server and i'm enforcing it the next time i see it

paper anvil
#

Ok fine sorry

candid yarrow
paper anvil
#

Photomath is still good though I did learn a lot from this

#

It gives detailed steps and explanations for each step

#

Chatgpt might be flawed like huh said though so my bad

obtuse pebbleBOT
#

@late flare Has your question been resolved?

obtuse pebbleBOT
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bright cosmos
#

Good evening/ day

My probability theory/ statistics is a bit rusty. I was hoping someone could help me with the following problem, where I need to decide on a sampling method to minimize the overlap between sets.

I am a teaching assistant who needs to feed 600 student submissions to a specialized plagiarism-detection software. Unfortunately, the plagiarism detection software only allows me to process 100 submissions per day. The plagiarism detection software has no memory of the previous submissions and therefore only considers comparisons between each the 100 submissions in a given batch. Therefore, I need to decide on a sampling strategy to minimize the likelihood of the plagiarism software not detecting plagiarism between two submissions. My idea was to use systematic sampling whereby I divide all submissions into k groups. Due to time constraints, I cannot create k sets, for a enormous k-value. Assuming the plagiarism detection software always detects plagiarism cases (since I will manually investigate all flagged cases to prevent false positives), is there a way I can minimize the likelihood of the plagiarism software not detecting plagiarism between student submissions?

My initial methodology was to divide the 600 submissions into k sets of 100 submissions each, such that each set is chosen to minimize overlap between all other sets. When a pair of submissions are flagged, they are removed from the original set and added to a flagged set. The flagged set will then later be used to check against all other submissions. This method assumes already-flagged cases will be more-likely to match with non-flagged cases.

Any suggestions?

Thanks!
Killa

bright cosmos
#

PS. The plagiarism software works by comparing submissions and producing a similarity score (expressed as a percentage) between each two pairs of submissions. If the similarity score is above a certain threshold, it is flagged for further investigation.

next reef
kind hawk
#

100 per day is a harsh restriction.

#

how likely is it that more than 2-3 people copy from each other

#

if you flagged some of them you probably already caught all the ones that did it

#

per group

timid silo
#

(the simplest solution is to ask your department to cough up money and get proper plagiarism software)

kind hawk
#

i mean even to check each assigment once this already takes a week

obtuse pebbleBOT
#

@bright cosmos Has your question been resolved?

bright cosmos
bright cosmos
kind hawk
#

how did you do it last time

bright cosmos
bright cosmos
kind hawk
#

how big are these assigments?

#

I dont even wanna know how often software flags code for plagiarism because two people use the same algorithm with the same obvious variable names

tame narwhal
#

"best-in-class scores" I'm sure that's the company's marketing speak 😑

bright cosmos
kind hawk
#

is there a size restriction for the software?

bright cosmos
bright cosmos
#

Well, I'm sure there's a theoretical limit. But the software is executed on Stanford's servers.

kind hawk
bright cosmos
#

Yes. That is what we are doing.

#

The other plagiarism detection leads to numerous false negatives/ false positives. We cannot solely rely on that -- too inaccurate.

kind hawk
#

(good that you mentioned that in your post btw)

timid silo
bright cosmos
#

Ok, thanks everyone. I'll do some reading.

#

.close

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late herald
obtuse pebbleBOT
latent fjord
#

show your work

obtuse pebbleBOT
#

@late herald Has your question been resolved?

obtuse pebbleBOT
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idle current
#

I was working on a question on a quiz about cylinders (can of food in the context of the question) there was 4 questions and one of the questions got me very confused. The question is "A can of beans has a Surface Area of x square inches. The can of beams also has a volume of x cubic inches, what is the value of x?" I have 0 clue of what to do and I didn't even try, after the quiz, I asked my classmates about the questions and they all responded with all different answers and saying that question was stupid. Any help?

knotty gulch
#

so

#

what are the formulae for both quantities

idle current
#

for SA it was 6pir^2

#

and volume was 2pir^3

knotty gulch
#

are you sure

idle current
#

yeah

#

the other question has nothing to do with the question i need help

knotty gulch
#

i need more context

#

is there any more

idle current
#

no

#

oh right

#

cylinder

#

it is a cylinder

knotty gulch
#

yes

knotty gulch
idle current
#

they provided with 6pi

#

thats what was given in the formula sheet

knotty gulch
#

6pi for what

idle current
#

it was written as "SA: 6pir^2" and "Volume: 2pir^3"

#

as the formula

knotty gulch
#

well the surface area of a cylinder is 2 pi r² + 2pi r h

idle current
#

yeah i looked it up after

#

but thats not what the quiz provided as a formula

knotty gulch
#

ok

idle current
#

thats literally the only context i can provide

knotty gulch
#

i’m not sure how i can help you then sorry

idle current
#

okay

#

.close

obtuse pebbleBOT
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steady patrol
#

hello

obtuse pebbleBOT
steady patrol
#

Sorry i didn't send the question here

#

if your free i'd like to hop on a call and for u to explain please

#

im desperate

obtuse pebbleBOT
#

@steady patrol Has your question been resolved?

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vale pilot
#

When a question asks for an angle in degrees "below the horizontal" does that essentially just mean I take away the negative?

vale pilot
#

I got to an answer in the 4th quadrant, -50.9061384 degrees

#

Would they want the answer just 50.9061384 degrees?

#

I'll round ofc I just copied and pasted it fromt he calculator

atomic hornet
#

yep!

#

below the horizontal means how far you rotate clockwise from the horizontal (initial line)

obtuse pebbleBOT
#

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golden current
#

hi everyone! 🫶

obtuse pebbleBOT
golden current
#

so on khan academy, i had questions in solid geometry to find the cross section of a solid perpendicular/parallel/diagonal to the base

#

im pretty good with knowing what the cross sectional shape will be parallel to the base

#

and perpendicular

#

but for diagonal, im not so good

#

like i just dont like visualising every time

#

it gets too confusing

#

and i cant really do it

#

is there a way i can know what the cross sectional shape of a solid will be diagonal to the base?

#

like proving it

#

not by memorisation

#

so that anytime i get a new solid, i can find the cross sectional shape

fathom flicker
#

if you had the shape, you could cut it yourself

golden current
#

yes

west sierra
#

Is it important to visualize, you can draw as well..(although I'm not knowing the topic you asked)

timid silo
fathom flicker
fathom flicker
golden current
fathom flicker
#

Could you send an example question maybe?

golden current
#

okay, brb!

fathom flicker
#

this lady doesn't provide much value because she is bad at cutting through foam somehow, but hopefully the idea isn't lost on you

#

this one might be better

obtuse pebbleBOT
#

@golden current Has your question been resolved?

obtuse pebbleBOT
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quasi harness
#

state the amplitude, period, phase shift and vertical displacement for the trig function with equation y= -sin(20 + Pi/3)-2 . Use this information to graph. Please show a graph for at least -2π ≤ θ ≤ 2π.
Choose appropriately sized scales.
I need help with this

whole dock
#

Period is $\frac{2\pi}{B}$

warm shaleBOT
#

ColdTee

whole dock
#

$Asin(Bx - h) + t$ is the general form, A is the amplitude, h is horizontal shift, t is vertical shift.

warm shaleBOT
#

ColdTee

quasi harness
#

yes

#

is the amplitude 1

#

@whole dock

whole dock
#

Yeah

quasi harness
#

vertical displacement 2 units downward.

#

whats the phase shift?

whole dock
#

Is that just 20

#

Inside the sine

quasi harness
#

what would it look like

#

-20?

#

@whole dock are you still there

whole dock
#

Should be 20x

quasi harness
#

20x?

whole dock
#

Yeah

quasi harness
#

I got -20 - π/3 units to the left.

whole dock
#

-2 becomes your middle line and the graph is between -2 + 1 and -2 - 1

quasi harness
#

can you show me how that would look like

obtuse pebbleBOT
#

@quasi harness Has your question been resolved?

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timid silo
#

Need help proving this

obtuse pebbleBOT
timid silo
#

I didn't write it but I already know U is a subspace. Also, every vector in S is in U tells me that U contains span(s), no? I need to prove the opposite

#

show that U and span S have the same dimension

#

Also, every vector in S is in U tells me that U contains span(s),
yes you are correct

#

but it seems to me that it is easier to show that U = span(S)

timid silo
timid silo
#

once you do that, you get equality straight away

timid silo
#

yes, its a very standard result

#

if a subspace has full dimension, then its everything

#

I see, thanks I will look it up

#

.close

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keen sonnet
obtuse pebbleBOT
keen sonnet
#

can i get some help just explaining this i haven't been paying attention in class and i just need to know how to solve tis

obtuse pebbleBOT
#

@keen sonnet Has your question been resolved?

keen sonnet
#

nope it hasnt

obtuse pebbleBOT
#

@keen sonnet Has your question been resolved?

craggy raptor
#

Since BC is a tangent, angle PCB has to be 90 degrees

#

and it should be straightforward to go from there

#

however ask me if you can't proceed

obtuse pebbleBOT
#

@keen sonnet Has your question been resolved?

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buoyant ether
obtuse pebbleBOT
buoyant ether
#

cant you just calculate the integral from here?

#

why does it split in partial fractal

#

can i not just say: 4/x²-4x+3 = 4*ln|x²-4x+3|

#

and 2x-1 = x²-x

#

x²-x + 4*ln|x²-4x+3|

empty hull
#

you cant

#

think of if you differentiated ln(x^2-4x+3)

#

since there is the chain rule it would be (2x-4)/(x^2-4x+3)

buoyant ether
#

ooooooooooooo

#

let me proces 3 seconds more

#

so i have to split into partial fractals

#

am i correct if i said: When there is a kwadratic function under the line (idk what is called for fractal) your answer never would be a ln||?

#

no ok its ok i understand

#

thank you

#

.close

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buoyant ether
obtuse pebbleBOT
buoyant ether
#

when can i know if there is a rest?

#

A/B =========>>>>>>> Q + R/B

#

rest is R

#

this Bx + C should only be added when you know there is a rest

#

but how do i know there will be a rest?

fathom flicker
#

what do you mean by "a rest" ??

#

the
"Bx+C"
Term comes from when there is a irreducible quadratic factor

buoyant ether
#

yes irreducible that is what i mean with rest

#

in belgium we call it rest, now i know irreducible quadratic factor

#

so how do i know there will be an irreducible quadratic factor

fathom flicker
#

look at your question

#

you see x^2+4x+5

#

can you reduce it?

#

if not, it is irreducible

#

x^2+4x+5 doesn't factor into linear factors

#

so it is irreducible

buoyant ether
#

OOOOOOOOOOOO

#

a quadratic cant be reduced?

fathom flicker
#

quadratics can be reduced

#

but some can't

#

for example

buoyant ether
#

like here for example there is no irreducible

fathom flicker
#

x^2+4x+4

#

can be reduced to

#

(x+2)(x+2)

#

but x^2+4x+5

#

can't be factored into two linear factors

buoyant ether
#

ah yes

#

how do you call the number under the line of fractal?

fathom flicker
#

the denominator?

buoyant ether
#

thx

#

so the denominator should be a line

#

if its not

#

then there is a irreducible factor

fathom flicker
#

In your denominator, you want to reduce it to as many linear factors as possible

#

linear factors contain a "x", not any x^2 or higher terms

buoyant ether
fathom flicker
#

if there are terms containing x^2 or higher degree polynomials that cannot be reduced, then these are irreducible

fathom flicker
#

if you have x^2, or x^3 ....

#

it isn't a line

#

any "x" is

#

5x, 10x, 1/2x

#

still lines

buoyant ether
#

aaaaaaaaaaaaaaaaaaaaa ok ok ok ok ok ok ok respect man

#

thx

fathom flicker
#

no problem

buoyant ether
#

.close

obtuse pebbleBOT
#
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bold siren
obtuse pebbleBOT
bold siren
#

how I would like to ask how 0.0228 come from

#

I did a) and calculate the calue of the test statistic is z=-2

#

and I checked the z score table is 0.4207

tardy epoch
#

two tailed z table probably

#

or just double/halve your test statistic

bold siren
#

it is a two tailed one

#

but having and doubling doesnt help to get the culmlative one

#

i tried both -1 N -4

tardy epoch
tardy epoch
bold siren
#

OH NO

#

i mislook the -.2 and -2

#

smh

#

thankss

#

.close

obtuse pebbleBOT
#
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ionic summit
#

This is a practice problem =3

Not sure how to do this one. The current understanding I have is that if two lines are parallel then the cross product is zero.

ionic summit
#

I was also thinking that maybe if the plane contained the line it would be parallel but thats not true either

#

this makes no sense

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what the heck

#

i guess im thinking of this wrong

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im thinking that the line has to be parallel to the plane such that like the edges of the plane (that i guess does not exist) are parallel to the line

balmy mortar
ionic summit
#

ye

balmy mortar
#

yes, if 2 vectors are parallel their cross product = 0 vector

ionic summit
#

the only way i suppose it cant be parallel if its pointing in like another direction like if the plane was on the x-y plane and the line was x-z or something

buoyant zealot
balmy mortar
#

you're checking for parallel planes. 2 planes are parallel iff the normal vectors to the planes are parallel

ionic summit
ionic summit
balmy mortar
#

Oh I misread.

ionic summit
#

well

#

yeah i think i was just mis intepreiting

#

like if the plane contains the line

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then its parallel

balmy mortar
#

In which case, you can check if the vector in the direction of the line is perpendicular to the normal vector of the plane

balmy mortar
#

I mean well

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The plane doesnt have to contain the line

ionic summit
#

i guess above or below it

balmy mortar
#

if the line doesn't intersect the plane anywhere, they are parallel

ionic summit
#

aswell

#

idk i had the misconception

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for some reason i thought like the line had to be parallel to the edges of the plane

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but that makes no sense cus it goes off forever

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but y'know when like u are taught

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what a plane is and its a fat square on the chalkboard

buoyant zealot
#

red is director vec of line
blue is normal vec of plane

ionic summit
#

ye

#

it makes sense now

#

okay

#

next step

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(I hope i get to draw the cat)

#

do they intersect

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perhaps

#

lemme think what to do

#

uhh hmm

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i guess to set the direction vector equal to the plane

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and see if there is a solution

buoyant zealot
ionic summit
#

i understand that :3

#

im trying to figure out if they intersect

#

well how to figure out if they do

#

supposedly

#

i just plug in the parametric equations into x,y,z into the plane

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and solve for t

#

would my method also work

buoyant zealot
#

yess that is the questions intended solution

#

if they do intersect all

buoyant zealot
ionic summit
#

would my method of

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setting the vector equation to the plane equal to eachother still work?

#

wait

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like

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hold on im not thinking

buoyant zealot
#

never heard that before xd

ionic summit
#

i understand now!!

#

thank you!!

buoyant zealot
#

glad i could direct you to understanding

ionic summit
#

🙂

#

.close

obtuse pebbleBOT
#
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steady owl
#

hey guys, i need help solving the following integral:

steady owl
balmy mortar
#

partial fraction decomp?

obtuse pebbleBOT
#

@steady owl Has your question been resolved?

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opaque galleon
#

sinx = cos2x
how to solve this algebraically because I ain't allowed to say "oh that's pi/6"

warm shaleBOT
opaque galleon
#

wow

#

RGB

warm canopy
#

you've got yourself a quadratic in sin(x) now

opaque galleon
#

.close

obtuse pebbleBOT
#
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warm canopy
#

okay?

opaque galleon
#

.reopen

#

yes

obtuse pebbleBOT
#

opaque galleon
#

( 1 + sqrt(2) sin x) ( 1 - sqrt(2) sinx)

opaque galleon
desert sinew
# warm shale

Think about it, from this you can get

$$\sin x = \cos 2x$$
$$\sin x = 1 - 2\sin^2x$$

warm shaleBOT
#

jimmy1234

desert sinew
#

Then how will you go about solving that? 🙂

opaque galleon
#

all good now

#

i can do it now guys dw

#

.close

obtuse pebbleBOT
#
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warm canopy
#

"thanks for trying to help!"

obtuse pebbleBOT
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timid silo
obtuse pebbleBOT
timid silo
#

why is lambda = 1/5?

warm canopy
#

because the mean of an exponential distribution is 1/lambda

timid silo
#

so its because when you find lambda it should be on a per/rate basis?

#

also how do I do 2.3?

desert sinew
# timid silo why is lambda = 1/5?

Thats just how exponential distribution behaves.

Quick ref in case you don’t have this in your notes or textbook: https://en.m.wikipedia.org/wiki/Exponential_distribution

In probability theory and statistics, the exponential distribution or negative exponential distribution is the probability distribution of the time between events in a Poisson point process, i.e., a process in which events occur continuously and independently at a constant average rate. It is a particular case of the gamma distribution. It is th...

obtuse pebbleBOT
#

@timid silo Has your question been resolved?

obtuse pebbleBOT
#

@timid silo Has your question been resolved?

obtuse pebbleBOT
#

@timid silo Has your question been resolved?

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timid silo
#

I believe those are the answers hmmCat

#

To get other answers you would just add or subtract $$2n \pi$$ to them. but that's outside the range of the question right?

final hornet
#

yea i think thered be 2 solutions within the range

warm shaleBOT
#

Brandon H

final hornet
#

oh

#

can i see your work

zenith raft
#

idt those are right

#

also i think there should be 4 solutions

#

what’s 0.71 from?

final hornet
#

probs 0.91?

zenith raft
#

what did you get out of the quadratic formula idea?

#

like… what did that lead to

#

why are you giving decimal approximations?

timid silo
#

they're probably using a calculator

final hornet
#

i got (6±√12)/12

zenith raft
#

same thing?

final hornet
#

think so

#

yes sorry

zenith raft
#

it’s ok 🙂

#

so you want x’s such that sin(x) = (3+sqrt(3))/6

#

so taking arcsin gives you one

#

can you see how to decribe the others if you look at the graph of sin?

#

what’s reference angle?

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ok sure

zenith raft
#

but that’s only “half” of them and it’s missing the one that’s approximately 2.234

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which is one that you want

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following?

#

ok so let’s let arcsin((3+sqrt(3))/6) = t so i don’t have to write that again

#

can you see the one you’re looking for is pi/2 (that’s where the peak between them is) plus the distance between t and pi/2?

#

yea i guess you could go through the same thing on the unit circle

#

i can’t really draw anything rn

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but umm

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if you take a point on the circle

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and then ask which angles take you there

#

one of them will be arcsin of the y value of the point or something

#

but just call that angle theta

#

the other one will be -theta + pi

#

you’ll probably need to draw it to see

obtuse pebbleBOT
#
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pure walrus
#

I’m looking for metrics that could be potentially useful for quantifying and comparing graphs. I don’t know a lot about graph theory but the problem I am working on can be translated into a comparison of simple graphs that can be either connected or disconnected, where the number of nodes is always the same. One metric that is somewhat relevant is the total number of edges.

obtuse pebbleBOT
#

@pure walrus Has your question been resolved?

timid silo
#

or graphs as in trees

obtuse pebbleBOT
#

@pure walrus Has your question been resolved?

obtuse pebbleBOT
#
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fathom flicker
obtuse pebbleBOT
fathom flicker
#

Hi, I am working on proving the statement in white. My idea is to do something along the lines of the blue sketch

#

my problem is, other than sketching that, I'm not sure what to do. Is that even the right idea? I might be overcomplicating this tbh

royal basin
#

is this your handwriting

fathom flicker
#

yeah I can type if you want

#

sorry

royal basin
#

no thats not the issue

#

the issue is that you arent writing \in properly

fathom flicker
#

yeah I don't know that one

royal basin
#

it's supposed to be a flattened C with a tongue, not an epsilon

fathom flicker
#

$\notin$

warm shaleBOT
#

AustinU

fathom flicker
#

like this?

royal basin
#

that's $\notin$, not $\in$

warm shaleBOT
royal basin
#

i'm talking about ∈

fathom flicker
#

oh

ruby path
#

omg blackboard

#

Respect

fathom flicker
#

my epsilon and in are bad

#

I am just bad at writing them differently

#

sorry Ann

#

There is no epsilons in the sketch so far though I'll tell you that

royal basin
#

anyway your idea is meh

fathom flicker
#

fair

#

Do you have any suggestions on either improving my idea, working forward from it, or perhaps a different idea?

royal basin
#

do you know how to show the existence of a rational between two real numbers

fathom flicker
#

yes

royal basin
#

do you also know how to show the existence of an irrational between two rationals

fathom flicker
#

No, I don't think I do

royal basin
#

try doing that then

#

then you will be able to reason as follows:
LEMMA 1. between every two reals there exists a rational
LEMMA 2. between every two rationals there exists an irrational
THEOREM. let x, y ∈ R s.t. x < y, then there exists an irrational between x and y
PROOF: by lemma 1 there exists a rational q s.t. x<q<y and again by lemma 1 there exists a rational r s.t. q<r<y, then by lemma 2 there exists an irrational i between q and r...

fathom flicker
#

Yes okay nice. I was definitely overcomplicating it

#

trying to work supremums into everything

#

I need to prove the existence of an irrational between two rationals then

#

I will work on that

#

ty Ann

muted holly
obtuse pebbleBOT
#

@fathom flicker Has your question been resolved?

fathom flicker
#

Okay, I think I have figured it out

#

If I have proven density once before, is it something I should be able to reprove at whim?

#

I don't think that I could do it without looking at notes

#

but, since I have proven it before I used that proof to finish this one

#

.close

obtuse pebbleBOT
#
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fathom flicker
obtuse pebbleBOT
fathom flicker
#

I am having trouble considering what this function is doing. To me it looks like it is making every x into f(x)=0.222222.....

#

but I must be seeing it wrong

zenith raft
#

isn’t f just taking the “locations” where the digit is 2?

#

the j’s such that d_{-j} is 2

fathom flicker
#

and doing what with them?

#

keeping them?

kind hawk
#

puts them in a set

#

a subset of N

#

aka an element of p(N)

zenith raft
#

send x to a set containing all the “locations”

royal basin
#

f is a set-valued function

fathom flicker
#

so for like x=0.1212, f(x) takes the 2 and 2 and places them in sets? So f(x)={2} and {2} ?

kind hawk
#

f(x)={2,4}

#

(not that this x is in E cause after that it continues as x=0.121200000..)

royal basin
#

0.1212 isn't in E

fathom flicker
#

0.1212000000...

royal basin
#

0.1212111111... is in E and f(0.121211111...) = {2,4}

fathom flicker
#

oh right

#

and

#

okay

#

I understand now

#

Thank you everyone

#

Okay so I am now trying to prove injectivity for that function

#

Does the following sound good?

#

so, f(x1) = {a,b, ....... n}

#

f(x2) = {c,d, .......m}

#

if f(x1)=f(x2) then f(x1) is a subset of f(x2) and vice versa

royal basin
#

notation is already meh

fathom flicker
#

why?

#

I did mean to put an m for the last element of f(x2)

royal basin
#

{a, b, ...... n} at best is a set of cardinality 14