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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
this following step is the step that I am lost at, I don't see where it comes from
AustinU
Any help understanding where this final equality comes from would be appreciated. Please tag me if you respond.
Køter
and im assuming the the real implication then is that that is < epsilon/2+epsilon/2=epsilon
showing x and y are epsilon close for some m1 and m2
@fathom flicker
ohhhh
because that's 0
gotcha
I was just wondering where those pieces came from lol
yeah, that is what happens next in the proof
triangle inequality
and then we show that |x-y| < epsilon for all positive epsilon
so x=y
Ty Koter!
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Can some one help with question 1
!status
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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
find out how big a fraction of the profit comes from the jumping castle
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how to prove with part one of FTC
How to prove what?
Alright, what do you mean by part one of FTC btw?
According to FTC, y = F(1) - F(1 - 3x) where F'(u) = u^3/(1 + u^2)
So y' = -F'(1 - 3x) * (-3) or simply 3(1 - 3x)^3/(1 + (1 - 3x)^2)
ok so
basically factoring the negative flip the upper bond and the lower bond of the intergals upside down?
Yes
that applies to every intergrals?
Yes
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!status
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
Yeah
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)
I am trying to learn to be more rigorous
Is there something I should change here to do so?
That is not enough
You just said f(0) = 0 and f(x) -> 1 at infinity
Which does not mean the range is [0, 1)
Instead you just need to prove the inequality 0 <= x^2/(1 + x^2) < 1 for all real x
0 <= x^2/(1 + x^2) is always true because x^2 and 1 + x^2 are both nonnegative numbers
And x^2/(1 + x^2) < 1 is true because x^2 < 1 + x^2
I understand
But that is a verification that that is the range
How do I frame my answer
With respect to this
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
i think once we get an intuitive idea, we can just show that its that like Lonely Bean said
Ya sure 2 mins
$\frac{x^2}{x^2 + 1} = \frac{(x^2 + 1) - 1}{x^2 + 1} = \frac{x^2+1}{x^2 +1} - \frac{1}{x^2 + 1}$
Matchstick
that would be $1 - \frac{1}{x^2 + 1}$
Matchstick
Highly incorrect imo and the range is not even coming correct but i think this is how it would be approached
but that brings us to the same spot as before, we still have to go the same route
sorry i am on PC so can't use camera for photos
Here we start with assuming that x^2 is always greater than or equal to zero
I could do it with Sign Scheme method but x^2 will then nvr be -1
bcz root of -1 doesn't exist
I told you range is not even coming correct
we could let x^2 /(x^2 +1) equal to 0. find x in that case
and then we could use that x^2 > 0
that will do
bro are you solving ncert?
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
we could but i was told that wasnt enough
I am also in 11th currntly doing this chaptr from Cengage
for JEE
ahh
Why r easiest problems most difficult to prove
i dont know 
maybe we can since we have actually proved that range would be greater than orr equal to zero in all cases then we can use values of x to determine range
but if we use your solution with the two cases it is good as done
This would have been very easy if x^2 could be
-1
but that is not possible
Maybe we can put f(x) in a variable
I'll try this approach
put in what?
alr
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
This one is incomplete actually let me complete it
If you put y < 0 then also the solution will be -ve which goes against >= 0
1 and 0 are the roots of equations y and 1-y
called critical points
and we do not include 1 bcz the 1/0 is undefined
@timid silo Did u understand?
1 hour wasted, phew
i feel worthless
how did you find the critical points?
1-y = 0
Y = 1
y = 0
Critical points r points where these variables will change signs
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
There is a method called Sign scheme or Wavy curve method which is not in NCERT syllabus but is very helpful
where we put signs on the number line
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Ok if an airplane covers 7007 miles in 98 upon 35 hours how long did it travel in 1 hour
ok i simplified it to if a airplane cover 1001 miles in 14 upon 5 hours
Let the plane cover x distance in one hour
So if in 1 hour it covers x distance, what distance does it cover in 2 hours?
@lavish sequoia
x times 2
98x?
35x?
x upon 2
Can we write 0.5 as 1/2?
Yes
yea
So in 1/2 hours the distance covered is (1/2)x
yes
So can you now answer the distance covered in 98/35 hours?
im sorry i dont get it 😭
Okay can you write 98/35 as a decimal?
2.8 right
Yes
So the plane covers x distance in 1 hour
2x distance in 2 hours
So what is distance covered in 2.8 hours?
2.8x?
yes
So both the quantities 2.8x and 7007 are equal
2.8x=7007
Now you can solve for x
Which is required ans
oh thank you
Welcome
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I came across an interesting question that asks to express sqrt 2 as an approximation in fraction
or using the words of the question
"Deduce sqrt2 as 1/(2+1/(2+1/2.....)))
i understand that it is irrational so thereby cannot be expressed correctly as a fraction (at least not in a form we can count)
but how would u go about proving this
Do you have a pic of it?
@rich plume here
scope of my knowledge is yr11 highschool
im not too sure how different australian curriculum is to elsewhere
The RHS is an infinite repeating series below numerator
yep i recognise that
Assume this quantity to be x
just before u proceed more into the question
generally when it says deduce, u arent really meant to use the RHS
and supposed to generate it from purely elsewhere
if that makes sense
well you can use the rhs to understand the procedure of getting from the rhs to sqrt(2), and then in the actual answer write the same thing but backwards
ah ok
dang
thats quite neat way
so thereby every irrational number is expressable this way?
isn’t this ramanujan continued fractions?
i suppose that is true only for ones which are not transcendental
yep
god dang this cant be it man
im screwed if this shows up intest
T=T
i suppose its still doable without full understanding of the theorem above
thx for the help
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Hi how do i do qb ii
use the exponent rule a^n/a^m=a^(n-m)
and a^n*a^m=a^(m+n)
all correct
correct
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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 Has your question been resolved?
<@&286206848099549185> 
how are they defining "reliable"
and yes, some more context and showing the data would be helpful
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.
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.
"statistical significance" should not have anything to do w/ "reliability"
has your textbook and/or teacher defined "reliable" in this context
no they havent unfortunately
would it be simply whether the model has pitfalls or not?
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?
all models have "pitfalls", technically
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)
so they're not asking us to specifically predict a score (as they provided us this data), but rather assess the "reliability" of the model
so I guess they might be asking about the residuals, perhaps. y - yhat
yea that was one of my initial thoughts. I was thinking residual analysis, f-test, t-tests, and/or something with r-squared?
here's the residual plot.
those look fine IMO
yep, i also think that
what do you think about using an f-test?
does that indicate anything about reliability or is that just significance
or arethose two terms interchangable
I don't know what reliable means TBH. it should be defined by the book or teacher
what are TOV and NEWB?
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.
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"
you could possibly use the F-test as justification
since the denominator is the mean squared error
which is low relative to the total mean square
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?
multicollinearity could be an issue, yes. whether they are stat. significant or not doesn't
do you mind briefly explaining why stat significance doesn't matter?
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
right that makes sense. So it may still have an impact but cannot be distinguished from a statistical standpoint?
I don't know what "distinguished from a statistical standpoint" means
basically the contribution may not be captured by the p-value completely
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
statistical significance and "practical" or "real-life" significance are different things
yep thats what i was trying to get at, thank you
and just one last qucik question
the y-intercept is 19.881, does this make any sense for this regression model and its practical scenario of a basketball game?
that is the total points scored when all predictors equal 0
so... I'm not sure how that could be possible. because that would mean FG%, 3pt%, and FT% equal 0
and TOV=0, and NEWB=0 (which you said is after the new ball design)
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?
cut off?
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
yep but in terms of interpreting the intercept, how does that work since we only have NEWB=0?
since we have to set the predictors to 0
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
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"
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
just in the multiple regression case, it's when all predictors/independent variables are 0, including any dummy variables
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.
it does have meaning. NEWB = 0 is for games after the new ball design was introduced
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)
yeah. it definitely gets confusing with multiple predictors
right. So do you think its safe to conclude that the intercept doesnt really make sense from a practical/real-life relevancy viewpoint?
since having a 0 FG, 3PT, FT is really unlikely and unrealistic
yeah, I don't see how that could be the case
what do the data look like?
maybe some of the rows where NEWB=0
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
but yea none of it is really close to 0
oh right. so it's probably an interpolation of the regression line, and would be the value if all the other variables were 0
which won't ever happen in real life
so yeah, I'd say the intercept parameter is not sensible in this model
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"
anyways, thanks so much for your help bro. Helped alot, I appreciate it
@vestal island Has your question been resolved?
how did they get the f(t + 5) ?
what don’t you understand in #❓how-to-get-help
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question 8 b, i’m completely stuck, have no notes on this and have never done something like this. where do i start?
Do you know how to determine the equation of a line?
what do you mean by that? i might have not sure
Do you know how to find the equation of a line?
This is the equation of any line, and now you need to find m and c for these specific lines
right, but what i’m confused is that in 8 b the line is under 6
so it’s (0,-5)and what?
what would be the x
this is the y intercept
Next you need to find the slope, m
using rise over run?
Or you can use a few points and solve equations
how would i do that? not sure what u mean
As in you already have (0,-5)
y= mx+c
-5=0x+c
c=-5
m would be -1/2?
Where did u get that
as a sanity check, if the graph is going up, your slope should be positive
right right my ba
reverse for negative slope: graph goes down
rise over run
rise of slope = 3
run = 6
3/6 = 1/2
so answer should be y= 1/2 x -5?
not sure what this is i’m super confused now😭
Thats just another (x,y)
oh yeh yeh
Yep
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for the derivative of sin(x+y)
Please don't occupy multiple help channels.
no
why
first step is already wrong
distributive property
What’s your issue ?
sin isn't a magic value being multiplied tio (x+y)
this
Tell fast
Cos x + 1
sine is a funnction
Done
so how do i find the derivative
Do you know differentiation to begin with
also the derivative of 2y
2
people say 2 dy/dx
Stop letting us complete your homework
is it 2 y'?
no
i still dont know how to find derivative of sin(x+y0
Use chatgpt then
is it capable of solving everything?
Sin derivative is cos btw
Yes just ask it to explain in simple terms
Don’t have to ask here
<@&268886789983436800> slaysec being very intrusive, past logs/messages aren't desirable either
Chatgpt literally helped me in my math understanding for a whole sem
are you familiar with chain rule?
I didn’t have to ask people compared to before it came around
Yes correct
the x + y is the gx
(f(g(x))' = f'(g(x)) * g'(x)
can you apply that here
1
why
no
that what confuses me
Any variable derivative is 1
ignore them
?
they're feeding you all the wrong info
You’ve studied derivation ?
oh so its y'?
And differentiation ?
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"
so it should be cos(x+y) multiply 1+y'
Yes
cos(x+y) * (1+y')
i got it , thanks @high lily and @paper anvil
stop encouraging people to use photomath or chatgpt for the things they ask here slaysec
I learnt math that way and it’s good to encourage platform than discouraging others users
This is what happens when you use chatgpt. This is the precisely the kind of missinfo it would give you
It helped me why couldn’t it help him
I meant differentiation not derivative
!nosols
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.
when you differentiate y wrt x, you get dy/dx, not 1.
Ok sorry my bad won’t provide answers anymore
Said platforms will not do anyone good who is actually trying to learn things. Especially chatgpt even gets maths wrong a lot. Do not tell people to use it
But I learnt differentiation and integration that way no one taught me
I could understand faster than watching YouTube tutorials
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
Ok fine sorry
what are you going to do about this?
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
@late flare Has your question been resolved?
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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
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.
I think you should ask this in #math-pedagogy
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
(the simplest solution is to ask your department to cough up money and get proper plagiarism software)
i mean even to check each assigment once this already takes a week
@bright cosmos Has your question been resolved?
Will do. Thanks
Only had three such cases last time.
how did you do it last time
We do have access to other plagiarism detection software, like Turnitin, but it does not work well with code. The software associated with my question highly specialized, free, and produced best-in-class scores when compared to other plagiarism detection softwares. They don't even have a paid version, which is weird.
The method I described above and lots of manual checking. This time around, we are much more time constrained, unfortunately.
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
"best-in-class scores" I'm sure that's the company's marketing speak 😑
The file size varies from 2000 lines of code to 10000.
This software is quite accurate. We use base-code to exclude commonly used code from the comparisons.
is there a size restriction for the software?
The best-in-class-score was determined by an independent party published in a respectable journal. Also, the software is free, so they don't market it at all.
Nope, but combining submissions would not work according to the original paper they published
Well, I'm sure there's a theoretical limit. But the software is executed on Stanford's servers.
when you say "does not work well with code", what exactly does that mean. could you maybe use it to "preflag" stuff and then use the other one for a second opinion?
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.
(good that you mentioned that in your post btw)
reading around, it is possible to get a paid local version of moss if you email the author. this probably wont be useful for you this time, but might be worth getting for the future
Oh nice! Thanks for letting me know. I'll definitely pass it on to the department head.
Ok, thanks everyone. I'll do some reading.
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show your work
@late herald Has your question been resolved?
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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?
For SA and volume?
for SA it was 6pir^2
and volume was 2pir^3
are you sure
Thats the issue, thats literally what they provided
no
oh right
cylinder
it is a cylinder
yes
.
well
they provided with 6pi
thats what was given in the formula sheet
6pi for what
SA
it was written as "SA: 6pir^2" and "Volume: 2pir^3"
as the formula
well the surface area of a cylinder is 2 pi r² + 2pi r h
ok
thats literally the only context i can provide
i’m not sure how i can help you then sorry
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hello
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
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When a question asks for an angle in degrees "below the horizontal" does that essentially just mean I take away the negative?
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
yep!
below the horizontal means how far you rotate clockwise from the horizontal (initial line)
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hi everyone! 🫶
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
if you had the shape, you could cut it yourself
yes
Is it important to visualize, you can draw as well..(although I'm not knowing the topic you asked)
So your solution is to bake a cake?
which solids specifically do you have issue with?
this is always a handy solution
like triangular prisms
Could you send an example question maybe?
i literally cannot visualise lol
okay, brb!
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
In this video, we will visualize the cross sections created when a plane intersects 3D objects in various ways.
this one might be better
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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
Period is $\frac{2\pi}{B}$
ColdTee
$Asin(Bx - h) + t$ is the general form, A is the amplitude, h is horizontal shift, t is vertical shift.
ColdTee
Yeah
Should be 20x
20x?
Yeah
I got -20 - π/3 units to the left.
-2 becomes your middle line and the graph is between -2 + 1 and -2 - 1
can you show me how that would look like
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Need help proving this
one way to do this is to show that every vector in S is in U, then show that U is a subspace, then show dimensions match
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)
The end goal is really showing that, but I already prove that U contains span(S) and I wanted to show that span(S) contains U
.
once you do that, you get equality straight away
You can derive that from a therom or something?
yes, its a very standard result
if a subspace has full dimension, then its everything
I see, thanks I will look it up
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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
@keen sonnet Has your question been resolved?
nope it hasnt
@keen sonnet Has your question been resolved?
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
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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|
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)
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
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Hello
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?
what do you mean by "a rest" ??
the
"Bx+C"
Term comes from when there is a irreducible quadratic factor
when you devide with euclidian, but cant animore
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
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
like here for example there is no irreducible
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
thx
so the denominator should be a line
if its not
then there is a irreducible factor
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
i will remember this , but i cant imagine why
if there are terms containing x^2 or higher degree polynomials that cannot be reduced, then these are irreducible
linear = line
if you have x^2, or x^3 ....
it isn't a line
any "x" is
5x, 10x, 1/2x
still lines
no problem
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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
it is a two tailed one
but having and doubling doesnt help to get the culmlative one
i tried both -1 N -4
just look at a z table
-2 = -2.00
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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.
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
what the heck
i guess im thinking of this wrong
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
you can only take cross products of vectors
ye
yes, if 2 vectors are parallel their cross product = 0 vector
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
of course this makes sense.
this is the same idea of if 2 lines perpendicular the a line perpendicular to one is parallel to the other
you're checking for parallel planes. 2 planes are parallel iff the normal vectors to the planes are parallel
im sorry i dont understand what u mean
i thought it was a line and a plane
Oh I misread.
well
yeah i think i was just mis intepreiting
like if the plane contains the line
then its parallel
In which case, you can check if the vector in the direction of the line is perpendicular to the normal vector of the plane
yes
I mean well
The plane doesnt have to contain the line
i guess above or below it
if the line doesn't intersect the plane anywhere, they are parallel
aswell
idk i had the misconception
for some reason i thought like the line had to be parallel to the edges of the plane
but that makes no sense cus it goes off forever
but y'know when like u are taught
what a plane is and its a fat square on the chalkboard
if red and blue vectors are ortho then the line and plane are parallel
red is director vec of line
blue is normal vec of plane
ye
it makes sense now
okay
next step
(I hope i get to draw the cat)
do they intersect
perhaps
lemme think what to do
uhh hmm
i guess to set the direction vector equal to the plane
and see if there is a solution
if you want a hint say
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
and solve for t
would my method also work
try it out and see if you get a parameter
would my method of
setting the vector equation to the plane equal to eachother still work?
wait
like
hold on im not thinking
never heard that before xd
glad i could direct you to understanding
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hey guys, i need help solving the following integral:
partial fraction decomp?
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sinx = cos2x
how to solve this algebraically because I ain't allowed to say "oh that's pi/6"
you've got yourself a quadratic in sin(x) now
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okay?
✅
( 1 + sqrt(2) sin x) ( 1 - sqrt(2) sinx)
okay?
Think about it, from this you can get
$$\sin x = \cos 2x$$
$$\sin x = 1 - 2\sin^2x$$
jimmy1234
Then how will you go about solving that? 🙂
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why is lambda = 1/5?
because the mean of an exponential distribution is 1/lambda
so its because when you find lambda it should be on a per/rate basis?
also how do I do 2.3?
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...
how do I do 2.3
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@timid silo Has your question been resolved?
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I believe those are the answers 
To get other answers you would just add or subtract $$2n \pi$$ to them. but that's outside the range of the question right?
yea i think thered be 2 solutions within the range
Brandon H
probs 0.91?
what did you get out of the quadratic formula idea?
like… what did that lead to
why are you giving decimal approximations?
they're probably using a calculator
i got (6±√12)/12
same thing?
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?
ok sure
so one of the solutions is arcsin((3+sqrt(3))/6), and that plus multiples of 2pi
but that’s only “half” of them and it’s missing the one that’s approximately 2.234
which is one that you want
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
but umm
if you take a point on the circle
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
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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.
@pure walrus Has your question been resolved?
graphs as in graphs of functions
or graphs as in trees

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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
is this your handwriting
yeah I don't know that one
it's supposed to be a flattened C with a tongue, not an epsilon
$\notin$
AustinU
like this?
that's $\notin$, not $\in$
Ann
i'm talking about ∈
oh
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
anyway your idea is meh
fair
Do you have any suggestions on either improving my idea, working forward from it, or perhaps a different idea?
do you know how to show the existence of a rational between two real numbers
yes
do you also know how to show the existence of an irrational between two rationals
No, I don't think I do
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...
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
does it require the chain rule
@fathom flicker Has your question been resolved?
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
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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
isn’t f just taking the “locations” where the digit is 2?
the j’s such that d_{-j} is 2
send x to a set containing all the “locations”
f is a set-valued function
so for like x=0.1212, f(x) takes the 2 and 2 and places them in sets? So f(x)={2} and {2} ?
0.1212 isn't in E
0.1212000000...
0.1212111111... is in E and f(0.121211111...) = {2,4}
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
notation is already meh
{a, b, ...... n} at best is a set of cardinality 14