#help-36
1 messages · Page 281 of 1
yes
in 6 days
haha
its ok
ah shit
hm
pff
was soll ich sagen
welches von den 3 wird mehr bewertet
analysis, geometrie oder stochastik
geometrie oder
boah keine ahnung
warte kannst du das nochmal erklären mit f(2)
denn sonst
ja also
ja erklär mal
star are you also german
ja
crazy
also f ist die ableitung der gesuchten funktion
f zeigt die steigung von F
ok bis jetzt?
ja
ja
ahh okay
ok berechne mal f(2)
-3
nein ich mene
oder
k
also F sollte die steigung -4 an der stelle 2 haben
guck mal auf den graphen
welcher passt
<@&268886789983436800>
genau
-4 heisst ziemlich grosse steigung
steiler graphen
aber die steigung kann man nicht ablesen direkt oder?
kannst sehen das rot weniger steil ist als II
doch
ja klar
zb bei x=4 ist die steigugn positiv
könnte man die funktion integrierenn
klar
und dann schauen was vor x^4 steht
versuch's einfach
ja mache es gleich
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How do i use Π with the line on the top longer
this? $\prod$
MxRgD
Ye
Ok how does it work
Do you know $\sum$ symbol?
Alberto Z.
instead of adding just multiply. that's all
It's the abbreviation of logarithm, which is the inverse function of an exponential
a^b = c
so, log(a)(c) = b
basically, a should be raised to the power of b to obtain c
!done
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lol
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how and where does this question allude to using methods of differences to find part a 
Partial fraction decomposition
Realise that the denominator of that fraction can be factored
how would u know to do that?
Thats like number 1 thing you check with sums
Check for a telescoping sum
ohhh
okok my brain immediately went to the standard form part of summations like just somehow using the identities for r = 1/2n (n+1) etc, but i couldnt see how u would be using it for this case
thankss!
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How do I get the intercept and slope from summary(linear regressional model)
Show the context you have
Lemme know if u can help or not
I'm guessing B Bar naught is 1.708e+2
And that B Bar one is 5.232e-03
Therfore 1.708e+2 + 5.232e-03 x 174mm
The answer would be 171.7104
Or rounded 172
@vital crag mate
What do u think
<@&286206848099549185>
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this seems good if you want more precision there is a method for that in R : predict(model_object, values_to_predict)
Alrighty thanks
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I want to calculate the work done $\int_S \vec F(\vec r) \dd \vec r$ with $\vec F = (x + z, z, x + y)^\top$ and $\vec g(t) = (3, 0, 6t)^\top$ along the striaght path from $(3, 0, 0)$ to $(3, 0, 6)$. Does $$\int_0^1 \sqrt{(3 + 6t)^2 + 36t^2 + 9} \cdot 6 \dd t$$ look fine?
ILikeMathematics
@unkempt prism Has your question been resolved?
\prpl I dont think you are supposed to take the magnitude, the formula was
[ int_{C} mathbf{f} dotproduct dd{mathbf{s}} = int_{alpha}^{beta} mathbf{f}(mathbf{g}(t)) dotproduct dot{mathbf g}(t) dd{t}. ]
Yes but then what is f(g(t))?
f is a vector
Then I would get a vector as work done
dr is also a vec
g dot t also is
oh
more specifically, they both create a dot product
So you end up with a scalar magnitude
aka, work
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Here I suppose I'd want the two sample t-test?
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✅ Original question: #help-36 message
So here if I can't assume equal population variances, but given the small population size what test do I use
the Z tests require sample sizs of atleast 30
dont you do x-y and find the pooled mean and variance
To get the distribution you want to work with
hmm? but here the groups are indpendent
so it's not a pooled test
oh pooled
not paired
I don't get this though, for pooled variance we assume equal pop variances
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If an ant walks from the base of a right cone to the other side of the cone, what is the shortest "walk" the ant makes. Given that the base of the cone is pi units long and it takes a total of 4 units to walk up the cone and back down?
I am sorry, I do not have the exact question/wording. The shortest "walk" i've found is a parabolic shape which is slanted on the cone but im not sure how to find the length of said parabola (if that is the correct method)
other side of the cone?
i think the path you found is correct-
yea but idk how to find the length of it
flatten the cone
-# yes but then the shortest path would be straight across which isnt what we want here..
huh?
but that straight line becomes a parabolic shape since the 3d surface is compressed into 2d - when extended back into 3d
yes..

-# woah nice i didnt think of this
yea make a net of the shape was one idea i had
well kind of
but same problem, idk how to find the distance
chord segment
well ik what it is but idk any relevant formulae
well first off, what's the length of the big chord
the big chord?
the red one here
yeah...
pi unit long
are they referring to the radius, diameter
or the perimeter?
i honestly dont know, the "base" is pi units long so i assume the circumference
since the ant cannot walk underneath the cone
or through it
remind me what subtended means
there is a formula for length of a circular arc
You can find alpha using that formula
mhm
so depending on what the question means by 4 units to go up the cone and back down
so either the slant height l (in this case) is 2
or the distance from the base to the apex is 2
it's the former I believe
mhm that would make more sense
since ant cannot walk through the cone
so if r = 2 and l = pi, then theta = l/r
so pi/2
or 90deg
keep it pi/2, you don't have to convert it
well..., yeah? cuz start and finish are at the opp side so yeah
mhm ok
ok so we make a triangle thingy
we know one angle and one side
and it meets at 90deg to the base as well right?
is we draw a line from the apex to the base
we actually know 2
Sorry I'm having food atm
its allg
do tell (when your free ofc)
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can someone explain when you write +C when integrating?
You basically always do
but when you have integration bounds, C cancels away, so we never write C in ther first place and just omit it
there could be a constant when you integrate yk?
think about differentiating a constant, it gets removed, which means when integrating you don't know whether there was one or not
wait so
yes this makes sense
but how do u figure the constant out
if there was some normal number
like 5
bro im so stupid
we have definite integrals for that, indefinite have +C
i forgot everything
ohhh
right yeah
usually they give you a coordinate and you plug it in
that the equation passes through
indefinite integrals means to find what was your original equation
it's actually professor propaganda to make you lose points in the exam when you accidentally didn't write +C /j
yes
i hope u understand now
yeah i gotta take a look at it again ill just do vectors and that stuff now
i mean i dont even know
how to study
alr you got worksheets on it?
alr if u need help send it here
like should i learn a thing till im perfect at it or do i just look at it a couple of times
ochem tutor and redbull gives you wings
do a bunch of practice questions until you feel comfortable doing it
i have 5 days left to redo linear algebra analysis and probability
how comfortable are you with it?
like
is there much to learn/revise or
I don't mean to discourage but um
bro
im quite comfortable with probability and analysis
except some parts
that's fine
like hypothesis tests, or parameter stuff
and linear algebra omg
i know like 5%
and in addition
the first partof the exam is without calculator
i will
but you'd pretty much have to neglect everything
personally i'd focus exam questions
usually it helps familiarizing yourself w exam Qs especially if the prof is usually repetitive
-# ok so your cooked then if it's finals
I'm ngl I'm rooting for them
(same)
is combinations in probability and hypothesis tests and parameter stuff
no hes got this, 4 hours sleep every day and 20 hours study gives 100 hours of study
-# highkey impossible but like- oh no
lowkey don't neglect sleep
nah i got this im not stupid
um
I wanna ask smth so bad
yea
are you asking about nCr stuff
focus and lock in
what does this mean
oh
I imagine it's the parenthesis thing in the distributions and some other things
no like
actually yes mb
but there are like 10 formulas
that's nCr
it's usually for binomial distribution
yeah thats easy i got that
oh wait those r the parenthesis things
i had 100% on that part last exam
this?
yeah
you can write it as nCr instead
sometimes r instead of k but it doesnt matter
yeah
this is why I hate combinatorics and permutation we just make up notations and shi
like calculus, who even uses '
how many hypothesis tests have been taught to you
like 3
which ones
t-test?
You bascially want to abuse the symmetry of a normal distribution
when you are caculating probabilities
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hi im new to this chanel
if you need help, #❓how-to-get-help
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A lil confused on part c
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Would this how I do it pls
Sure. You could shortcut a little bit and use the Pythagorean identity directly as well instead of going to the foundations of right triangle trig.
What is that
$\sin^2 \theta+\cos^2 \theta=1$
Civil Service Pigeon
Sin(90-x)
sin(90-x) = cos(x)
And this
My teacher o my used the diagram one

?
don't forget to block them too
I gotta go in like 5 mins
?? who
me
u really wanna block me for saying this
do you mean a right triangle?
Yeah
that's valid as well
I can't tell if @loud sundial wants to block me or block @runic needle
wrong ping
Mb
what's ur final answer for sin50?
i mean, what u wrote is along the write lines
but there are inacuracies
I wasn't trying to snipe. If I did, my bad
how did you get x = p @tired osprey
I thought x was associated with sin
he said people, not person, so i probably both of us
What is snipe
dawg
do you know what right triangle we r talking about
maybe u should draw it
No
Probably. I rally didn't mean to, I was just confirming that sin(90-x)=cosx in my book. Pls forgive me @loud sundial
i think if you keep pinging him, it could make matters worse
Well i tried
No helper 'owns' the channel, so it's not that deep really
I think it is light etiquette
Ye but he seems pretty mad
this doesn't seem mad to me
I dont think they are mad
riemann seemed more mad tbf
yeah it says happy :D
Ye
@loud sundial was not exactly mad but more annoyed
You are, yes
Can I try again and show
Ok
u really testing it
Fine fine. But I rlly shldnt be texting now
Whats the worse that can happen
??
Youre just cluttering this person's help channel by this point
Ur right mb
I'll stop now
Now you just find x/r
You should not be writing sin(50) = p/1
That's p/r
The problem gave you sin(40) to work
Why
r = 1 so works both ways i guess
I’m confused
i think decide this first then proceed
I have a question why do you take long time at this question you can approach with identity sin^theta+cos^theta =1 then approach with formula sin(90-theta) that's simple
That's exactly what they're doing gang
read the channel twin
Simple for you. Not for her
Ok broo chillin
Not everybody knows this by default
can you stop invading other people's channels with insulting comments. thanks
yall let one person help out, having 3-4 people trying to say different things is overwhelming for the student
Agreed. Ill stop
i'll stop as well
Because it's become too much messy for her
And sorry i do not insult anyone in channels
we could let op decide who she wants to continue helping
Ok
It's a good idea to visualise it. Can you draw a triangle real quick with edges x, y, and r and the angles 90, 40, and 50?
Ok
Do I always draw a triangle
So. What is sin(50) in terms of x, y, and r only?
Y over r
Awesome
So
What about sin(40)?
Again, only in terms of x, y, and r
Yes you should
X over r
Alright lets notice something
I can understand doing the sin but not the cos
Can you explain?
I am just trying to explain to you the relationship between all of them with x, y, and r since you were confusing that primarily
Ohh
Basically,
you now know that sin(40) = x/r and sin(50) = y/r
Since you are given sin(40), you should have x = p (since r = 1)
And then do the same steps you did already
I don’t get it
This
The second sentence
maybe it'd help if you wrote out sin(50) and cos(50) in terms of x, y, and r. then the same for sin(40) and cos(40) to see what lex is saying
She already did haha
sin(40) = p, right?
Your problem says it in thr first sentence
Yes
ok
Yes
Yes
r = 1, agreed?
Yeah to make it a fraction, I think
Idk what that means but r = 1 because fhis is a unit circle
So p over 1
Oh
Uhuh
Do you still not get that second sentence now?
I get it now
Nicee
So then I find y?
Yuh
can I do it an show you
You already did it!
The work here is pretty kuch correct, its judt that your variables were assigned incorrectly
But you csn still show me
Degrees?
Angles
Wdym
Reread the conversation if you must but I feel like I shared everything i could share
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Btw are you the same skittle
Or is this like a very strange coincidence lol
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19
,rccw
!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 was told that it's wrong.
4. I got an answer and would like my work checked.
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6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
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Interesting
Asked the question, rotated it, stated the status, and solved it themselves
They just needed a new perspective
ayo man
I know, it was a joke
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Hiii
use k! = k * (k-1)! and this
you're supposed to start with induciton hypothesis, not the conclusion from induction
it might help to take the inequality you want to arrive at then reduce it to something you know is true
How do I do that
In the bottom left corner I wrote where I’m trying to get to
Oh wait
well you want to get to
(n + 1)! > (n + 1)^2 + (n + 1) yes?
It should be +2
yea you forgot to make the last part k + 1
was this middle bit you trying to get the inequality?
Yeah
it looks like you multiplied by k + 1
let me latex this
$(k + 1)! > k^2(k + 1) + k(k + 1)$
I did so k! Goes to (k+1)!
knief
mhm
Yh
now you want the right side to be (k + 1)^2 + (k + 1). we can factor to get k(k + 1)^2 like you did
we wanted to show it’s >= (k + 1)(k + 2) right
or
(k + 1)^2 + (k + 1)
Yesss
so you can simply divide both sides by k + 1 to get k(k + 1) >= k + 2
k^2 - 2 >= 0
which holds since k >= 4
What
ok i’ll show you in latex
we have $(k + 1)! > k(k + 1)^2$. we want to then show that [k(k + 1)^2 \geq (k + 1)^2 + (k + 1) = (k + 1)((k + 1) + 1) = (k + 1)(k + 2)] since $k \geq 4$ we can simply divide both sides by $k + 1$ to get [k(k + 1)^2 \geq (k + 1)(k + 2) \iff k(k + 1) \geq k + 2 \iff k^2 + k \geq k + 2]
knief
then subtract k from both sides to get k^2 >= 2
which is obviously true since k >= 4
if you aren’t comfortable with why we can divide by k + 1 then lmk
takes practice
if i see something that i can factor, i factor it
making it (k + 1)(k + 2) helped
Yep thx
no worries
like your original statement is really just (n - 1)! > n + 1
for n >= 4
divide by n
Yeah true
Hm
I have another kinda similar question too
Again like idk how to prove that 2k^2>(k+1)^2
i think this is supposed to n^2
can you show your work
oh you just
multiplied by 2
Yep
well try expanding this
collect like terms
Ohh
there are a few ways you can do this
Why do you include the =
because for transitivity we don’t need a strict >
if a > b and b >= c then a > c
sometimes it matters
I see
in other problems you might not get b > c
it might be b >= c
so i just make it a habit to use >=
even if equality doesn’t hold
anyways
do you have any ideas?
you can do this with algebra
or induction if you really want
Bring it over to one side and complete the square ?
nice
Is this ok
yea
i don’t know how strict your graders are
maybe they want you to show clearly why (k - 1)^2 >= 2 for k >= 5
but i’d accept that
How would I do that
just so you know,
yea
ok
k >= 5 implies that k - 1 >= 4 so
(k - 1)^2 >= 16 and so (k - 1)^2 - 2 >= 14 >= 0
easy enough right
these sort of statements that involve just simple expressions in terms of k can often just be manipulated/derived from the starting condition on k (here it’s k >= 5)
Cool this has been rlly useful
always keep in mind what we’re assuming is true
k >= 5 here is sort of our "base"
it’s the statement we take to be true then discover other true statements that follow from it
this is what math is about
given a certain set of true statements, what else is true if those are?
like in a sense, these are the same statements just in a different form
maybe not "same"
since they don’t both imply each other
but k >= 5 implies the other one
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what do you think
i am not sure
have you at least tried some examples
as in, have you tried some values of a and b
and found the gcd and lcm
i want to know why
d = gcd(a,b) => d | a , d | b => a = d.k , b = d.q
l = lcm(a,b) => ?
like which one
like gcd takes the minimum exponent from each prime power in the prime factorizations of a and b
for lcm we take delta_i = max(...)
isnt it complicated
no this is really quite simple actually
this is how you'd probably go about finding the gcd in your head in elementary school
have you not seen this before?
the proof i have in mind involves these definitions
yes this is usually how they first define it
usually you come across this definition shortly after
which imo is a better definition
it literally turns into proving min(n,m) + max(n, m) = n + m
mhm
to prove the statement we want to end up proving we just need to prove this
do you know which answer choice is correct btw
or at least have any guesses
D of course
so if we write [a = p_1^{\alpha_1} p_2^{\alpha_2} \cdots p_n^{\alpha_n}, \quad b = p_1^{\beta_1} p_2^{\beta_2} \cdots p_n^{\beta_n}] then what does $ab$ equal?
knief
in terms of the prime factorization
alfa + b
mhm
so
$ab = p_1^{\alpha_1 + \beta_1} p_2^{\alpha_2 + \beta_2} \cdots p_n^{\alpha_n + \beta_n}$
knief
y
now
are you saying and or why
ye
ok i'll assume you mean and
i Meb yes
now we need to find the prime factorization of gcd(a,b) lcm(a, b)
i'll use this notation ok
also let's say uhh varphi is max
like $\varphi_i = \max(\alpha_i, \beta_i)$ where $1 \leq i \leq n$
knief
can you tell me what gcd(a, b) lcm(a, b) is
like write the prime factorization
you don't have to write it entirely i guess
just in words
wdym
i wrote the prime factorization for ab
gcd = p1^phi
can you do that for gcd(a, b) lcm(a, b)
?
if we multiplied them what would we get
?
no we used delta for min
no
this definition is for gcd
you're ok with this though?
what about lcm
replace min(alpha, beta) with max(alpha, beta)
and you get lcm
we take the highest power of each prime
because we need it to be a multiple
for example the lcm of 2 * 3^3 * 5^2 * 7 and 5^3 * 7^2 * 11 is 2 * 3^3 * 5^3 * 7^2 * 11
we need it to be a multiple of each so it has to have at least as many copies of each prime from both
and since we don't add anymore copies of the primes we get the least common multiple
does this feel intuitive
for the gcd we needed it to divide both so we couldn't have more copies of any particular prime than one of the two numbers had individually, so we would take the smallest prime power for each prime
what is a multiple
a is a multiple of b is a = bk for some integer k
12 is a multiple of 4 since it's 3 times 4
a | b <=> b = a.k
a being a multiple of b means a is a divisor of b
on the one hand this says that a divides b, but on the other hand it says that b is a multiple of a
other way around. it means b is a divisor of a
how?
i have heard
so you agree with this?
and this
what do you normally say in spanish?
back when you were a kid learning about this stuff
multiplo
minimo comun multiplo
lcm
you agree with this?
yeah um just bad at mwth
the variables make it confusing
i hope we can agree that 12 is a multiple of 4 and 4 is a divisor of 12
is just max×min
wdym
surely
so this makes sense
ab = p^(max x min
well we said ab = p^(alpha + beta)
we are trying to figure out what gcd times lcm is
we had a detour
now do you agree that lcm(a, b) = p_1^(max(alpha, beta)) ....
like did this make sense
is p^min x p^max = p^min+max
yes
so we get p^(min + max)
and we are trying to show that it's equal to p^(alpha + beta)
so we simply show that min(alpha, beta) + max(alpha, beta) = alpha + beta
try this
lmk how it goes
how
don't overcomplicate it
what if min = max
you tell me
ah ten a+b=2a=2b
yep
ye
three cases a < b , b > a and a = a
min = a or min = b or min = a = b
care to elaborate
well the cases alpha <= beta and beta <= alpha are identical
it's just a difference in labeling
we can just say without loss of generality assume alpha <= beta
how
we are trying to show min(alpha, beta) + max(alpha, beta) = alpha + beta for arbitrary alpha and beta
alpha and beta are just any nonnegative integers in this context
they are just placeholders
like ok if you prove it for a < b
can't we just relabel a and b
a --> b and b --> a
the labels themselves are meaningless
integer one and integer two
wlog the proof is that min + max = a + b
yes
but wlog assume a <= b
maybe it would be instructive for you to do the extra cases so you can see what i mean
a < b
max + min = b + a = a + b the field Z is commutative under addition
a > b
mac + min = a + b ✅
a = b
a + b = 2b
✅
easy enough
yep
so ab = gcd x ñcm
enya
ñ = L
does it
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Hi I’m a bit confused on the second / third part
I may drop a hint for the first one(you've already solved it, this is for future problems): if $z$ is a root of a polynomial with real coefficients, then $\bar{z}$ is also a root.
Annie Maqionde
For the second part well you do know that:\
- sum of roots = $-a$\
- product of roots = $b$, right?
Annie Maqionde
For the third one you may reduce it to a quadratic by an appropriate subsitution, and then go forth and square root the roots of the resulting quadratic.
@raw patrol Has your question been resolved?
Ohh
I overcomplicated
It’s just 16+30i
Yeah my teacher also told us x^2-2Re+|z^2|
Hm
I still don’t fully get iii
Is it this
is this for part iii?
Yh
so $y^4 + ay^2 + b = 0$
KB
we dont know how to solve a general degree 4 polynomial (without massive formula) so instead lets make a substitution
let V = y^2
what do you notice about the new equation?
It’s a quadratic that we know the roots to
mhm
so your process is correct
so what in particular doesnt make sense
its just asking for the 4 roots to the equation no?
for my complex numbers test the other year a similar question was worth 8 marks i believe
Also in the markscheme they got + or - (5 + or - 3i)
thats just simplifying the square root
When I simplified it I got a different answer
let me quickly go over the question
Ok thx
what were the values you got for a and b
-32 and 1156
The main reason I’m confused rn is bc they got 5+3i whilst I got 5-3i for my root
this is what I got: $y = \pm \sqrt{-\frac{a}{2} \pm \sqrt{\frac{a^2}{4}-b}}$
KB
although, it may be that its pm, and then mp


