#help-27
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Mathematics
π tf am i supposed to do w that
No wonder I saw that in my poisson table thingy
How I get given for lambada
Lambda
$$P(X\leq 2)=e^{-3}(\frac{2+6+9}{2})=e^{-3}\cdot 17/2$$
Benjamin
Howd we get the 9
Where get nine huzz
You ask too many questions
It comes from 3^2
Oh ok that makes sense since fine shyt never gets mad at me fr
The Poisson probability mass function (PMF) is:
$$
P(X = k) = \frac{e^{-\lambda} \lambda^k}{k!}
$$
where ( \lambda = 3 ). Buddy, calculate:
-
For ( X = 0 ):
$$
P(X = 0) = \frac{e^{-3} 3^0}{0!} = e^{-3}
$$ -
For ( X = 1 ):
$$
P(X = 1) = \frac{e^{-3} 3^1}{1!} = 3e^{-3}
$$ -
For ( X = 2 ):
$$
P(X = 2) = \frac{e^{-3} 3^2}{2!} = \frac{9}{2} e^{-3}
$$
Cuh sum them:
$$
P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)
$$
$$
P(X \leq 2) = e^{-3} + 3e^{-3} + \frac{9}{2} e^{-3}
$$
Factor out ( e^{-3} ):
$$
P(X \leq 2) = e^{-3} \left(1 + 3 + \frac{9}{2} \right)
$$
$$
P(X \leq 2) = e^{-3} \times \frac{17}{2}
$$
Approximating using ( e^{-3} \approx 0.0498 ):
$$
P(X \leq 2) \approx 0.0498 \times 8.5 = 0.423
$$
Thus, the final probability is:
$$
P(X \leq 2) \approx 0.423
$$
Benjamin
Wtf is the squigle thingy
AHAHAHAHHSHDBDB
The double ~
Wtf bru I aint even using math in a farm
Alright
How does it feel to have the smartest helper help u
Thank you fine huzz ππ«‘
Np jit
Special fr πππ
Ofc I have a keen eye for things
Yah
Wanna see the frog I dissected? π₯° It's giving max level 10000 cutie fr
$$\mathfrak{yes}$$
Benjamin
Also the tilde means βis distributed asβ
Thank you π«‘
Yes
I sent it in your dms I'd send it here but I might get banned π
Okay
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Help
this is an ellipse, make the right hand side 1 first
latus rectum is the line that passes through the focus of an ellipse
are you required to show your working? there is a direct result that'll let you find the length directly
yea this
x^2/a^2 + y^2/b^2 = 1
No working just the use of formula
is the form of an ellipse
Root 12 is b ?
yep
Then the answer is coming to be 12
Which is not one of the options
Nvm got the answer tysmmm for the help tho I was using the wrong formula
β€οΈ
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Which one is the pivot?
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@desert girder Has your question been resolved?
You can use Polynomial Long Division to yield that exact format.
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Can someone please help me with this?
right
but they said it is 3857
so we know the squares in question can't have been the first 20 perfect squares
yeah
what if the first 19 were as low as possible? what upper bound does that place on the highest square?
if first 19 perfect squares as low as possible then their sum would be 1885. so the last one would be 3857-1885? idk
,w sum[k=1, 19] k^2
2470 surely
this leaves 1387
so the largest square can't be bigger than 37
yeah
yeah but it means we cannot have any square bigger than this, ever
so at least this narrows down the search space
must they be distinct?
yes
try to assemble a sum of 3857 using 37^2 as your largest?
i don't see anything cleverer here
When I get the answer for cos do I have to on calculator put the answer and than shift to get cos-ΒΉ to get the answer
!occupied
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maybe we can replace a perfect square in the first 20?
oh I got it
a^2 - b^2 = 987 => (a-b)(a+b) = 21 x 47 a = 34 b = 13. so largest is 34^2 right? or did i do something wrong @pseudo basin
hmm where are you getting a^2-b^2=987 from
i did 3857-2870
so i need to get a new perfect squre excluding the first 20, replace one of them
oh hm.
the new perfect square should be 3857-2870 more than the existing one
oh so you swap out 13^2 for 34^2?
idk
,calc 35^2 - 34^2
Result:
69
because in a^2 - b^2 = 987, u dont get any other prime factors such that one of them is <=20 and other > 20
3x7x47 yields 21, 47, 141,7 or 3,329
oh wait does 3,329 work then
no thats too big ig
so it IS 34? @pseudo basin
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i... guess?
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whats the difference between concave up and convex down? or are they the same?
never heard "convex down"
oh
usually it's "concave up or concave down" or "convex or concave"
it's either concave and convex or concave up and concave down
so theres no convex up or down
I mean if you want
its just concave (up) and concave (down)/convex
you could define it, but it's not standard so you would be less understood
but generally
concave up = convex, concave down = concave
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guys what is 2+2
Are you trolling?
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Help
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β
?
substitute $u=e^x$
strizz
and what i change the x into?
strizz u lowk ate and devoured with that pfp
ln u
we love paul
@gray bluff Has your question been resolved?
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Can someone help me with both of these question?
,rotate
Wait nvm for no 1 I got the anwser
So I need help with no 2
:v
by long division you get that $\frac{n^2+2023}{n+1} = n-1 + \frac{2024}{n+1}$
artemetra
so find all factors of 2024
._.
is there something that confuses you?
I'm trying to process this information π
to put it down, n-1 is an integer, because n is an integer. we need $\frac{2024}{n+1}$ to be an integer, in order for $\frac{n^2+2023}{n+1}$ to be an integer, so that $n+1$ divides $n^2 + 2023$
therealtdp
for $\frac{2024}{n+1}$ to be an integer, we need n+1 to be a factor of 2024
therealtdp
So uh n+1 is an integer and we need factor of 2024 so it can be divided by n+1
So then factors are 2,4,8,11,23,88,184,253,506,1012
n + 1 = 2, 4, 8........
well it just asks you to find the number of positive integers
so you just needed 2024 = 2^3 * 11^1 * 23^1
hence there are (3 + 1)(1 + 1)(1 + 1) = 16 positive factors
but this includes n + 1 = 1, so we exclude that and we have 15
you missed quite a few
Oh. ._.
Oh there's 16 total right
So uh
Missing 3
Uhh
2Β³ x 11 x 23
Let's see
1, 2, 4, 8, 11, 22, 23, 44, 46, 88, 92, 184, 253, 506, 1012, 2024
Ok so uh n = 1,3,7,10,21,22,43,87,91,183,252,505,1011,2023?
One of these?
yes
read the question again, it asks you how many n there are
not what the n actually are
just do this from the prime factorisation
you are choosing from
powers of 2: 0, 1, 2, 3
powers of 11: 0, 1
powers of 23: 0, 1
by the multiplication principle there are hence 4 * 2 * 2 = 16 choices
each choice gives a different positive integer, of course
Ohh honestly I knew this thing but I never knew why it worked xd
Ty
np!!
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Also could someone check if this is correct for number 4?
This is a clearer picture of 5
can you show that $\frac{u^4 + u^2 + 1}{u^3 -1}$ simplifies to $u + \frac{1}{u-1}$?
kizzyyy

Uhhhhhh
No idea
π
I was thinking of uβ΄ + uΒ² = uΒ³ + 1 but that's just untrue cus I was thinking of (n + 1)(n-1) = nΒ² - 1
Oh wait it's u from last time
mmm when all hope is lost
you can always do polynomial division
Oh I finally got it after so many tries π
Oh so 1/2022
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Can someone calculate and tell me what they're getting? I wanna check if I got the answer right or not
yours first
Well I'm actually getting two different answers π
show both of your answers along with working
very wrong indeed...

is that a new variance formula from outer space?
first off you should probably be working with the numbers 2, 3, ..., 11 unless you have enough foresight to tell that adding 1 won't affect the variance
Ann, I'm going to fail maths π
secondly you should find the mean of all these things
uh.
do you want to bitch/whine/vent/etc. or do you want to know how to solve this problem properly
at least look up the formula you've been taught to solve the problem
I want to know how to solve this
ok right
first off you should probably be working with the numbers 2, 3, ..., 11 unless you have enough foresight to tell that adding 1 won't affect the variance
secondly you should find the mean of all these things
these 2 points stand
I did, I watched a video too I'm so lost 
can you write down the formula you attempted to use?
just the formula in general, nothing plugged in yet.
Ann
Yeah, I got 5.5 however that's a big calculation, I don't wanna go through that so
Assumed mean
wdym "assumed mean"?
...subtracting and adding a value from the middle of the series that is closest to the mean?
i mean... ok?
but shifting down by that doesn't make the new mean 0.
you cannot just pretend that your mean is 5 instead of 5.5
that's not how it works
well you will have to deal with it anyway
I mean, I could do that but this is like an 80 mark paper with 3 hours to finish it
the fractions don't get any denominators worse than 4
you can sweeten the pill somewhat
your values of x - mean are -4.5, -3.5, -2.5, ..., 2.5, 3.5, 4.5
or -9/2, -7/2, -5/2, ... up to 9/2
which is not THAT bad
Yeah, I suppose it's not... π
Sighs okay I have like 23 more questions to go
So I'm going back to hell
See ya
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Can someone please tell me what type of function this is?
riemann
i get this
riemann
but what i meant is like how would i classify this function? like how we say that y=x^2 is a quadratic function, how would we call this one?
not all function types have a name
so this one just isn't classified?
those classifications you are thinking of only work for very basic examples
its way too easy to come up with functions which wont fit
this one being one of those
you might call it sublinear but thats more a property instead of a general "classification"
alright thank you π
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i tried to help someone but i kinda explained it badly
its one of the geometry rules
also i realized my mistake on the angles AED and CEB so just ignore that
what rule is it again
hmm ok i think i get why
its like reversed
same coresponding angle, parrarel lines cuz pararell lines = same corresponding angles
ok
thx
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anyone able to help with part 3 i dont get what it means
the damping term is $\gamma\dot{x}(t)$
Ann
compare the period with damping to the period without
@cerulean quarry Has your question been resolved?
Because T_0 is 1 is omega then 2pi and I use that to get a value for T_d
Along with my gamma from the 2nd part
@cerulean quarry Has your question been resolved?
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I donβt understand why my method (on the top) doesnt work with the actual answer (on the bottom)
its the same
Your solution is correct
due to all the trig identities, the same things can look very different
your expression is equal to 1/6-1/6cos^6(x)
It varies by a constant
so the same up to the constant of integration
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How do I prove x=10?
Also sorry for bad handwriting
Let me rephrase- how do I prove the question has only one solution?
Sorry there's a plus somewhere instead of minus
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How do I prove x=10 is the only solution for this?
Nevermind it's not even 10
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i was about to say
it's already closed
Oh
takes time to become free againn
Wait no it is 10 I just wrote the equation wrong twice

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im kinda confused on part i. Im not really sure how I should use the hitn
(how do you have being (not/) connected defined, btw?)
not connected is there eixsts open sets O1, O2 such that O1 U O2 supset K and O1 cap O2 = empty st and K not subset of O1 and K not subset of O2
The definition of connectedness involves two open sets, so it would be natural to try and use that
Suppose K is not connected. Then there exist open sets U and V such that Uβ©V is empty and K β UβͺV. now consider the sets K'_n = U^c β© V^c β© K_n. Clearly each K'_n is compact, K'_n β K'_(n-1) β ... K'_1, and the intersection of the K'_n are empty; This contradicts a property of compactness(which I assume you have already proven)
but how do we know that K'_n = U^c ...
ah are you constructing something new?
yep
basically as the hint said
ahhh wait okay. I think i mistinerpeted the hint and was trying to do some funny stuff with sets
each K'_n is compact since intersection of compact set ic compact right?
or intersection of compact with closed set is compact
and then we can apply that indutively
to as many closed sets + comapct set
oh wait also arbtiary intersection of closed set is closed
yes, because a closed subset of a compact set is compact
so here we actually dont need th eintersection to be countable (sry kinda going on tangent)
or i mean how we index
because it can be arbtirary
and in any metric space compact => closed + bounded
yep
so actually any intersection of compact + closed => compact
not just countbale index thing
that's actually only for euclidean spaces, not all metric spaces
All metric spaces, it's the converse you're thinking of
but how is their intersection empty?
misread it
isnt their inntersection oh wait
their intersectino is
O_1^c cap O_2^c cap K
but that isnt empty i think
ah shoo
wait
we have htat O_1 U O_2 supsetof K
this is empty since K β UβͺV was assumed at the start; in words, If K is included in U plus V, and you take away U and V from it, you're left with the empty set
so O_1^c cap O_2^c subset of K^c, thus O_1^c cap O_2^c cap K subset of emptyset
for part ii, using the hint and the fact it is in R^2, i think i need to find an unbounded and probably not closed set
im thinkin gof the set ${(x,y): x \in [0,1], y \in [0, n), (x,y) = (\frac{1}{n}, n) }$
LXDL
where the "connected" point that goes unbounded is 1/n, n
There's a lot of approaches for this one, just make sure to satisfy the 'nested sequence' part
an unbounded U-shape like R^2 minus [-1, 1] * [n, inf), with n getting larger, is one simple example
ah okay, but here that set is connected?
because i think it looks disconnected since once cannot reach inf
or ig i would try a proof bu contradiction approach
maybe
Oh it's supposed to be [-1, 1]*[-n, inf), my bad
wait but then its no logner nested
the way I originally wrote it, it wouldn't even be a nested sequence
the sets are R^2 - [-1, 1] * [-n, inf)
because we have $K_1 \supset K_2 \supset K_3 \ldots$
LXDL
yes, in fact, [-1, inf) is a subset of [-2, inf)
but I'm not using those sets but rather their complement with respect to R^2, and the complement of [-2, inf) is a subset of the complement of [-1, inf)
think of something like this, where the square is R^2 and the shaded area represents each set K_n
(excuse the horrible drawing)
ahh okay
ohhhh
waut
and its like
the line divicing the middle
makes it eventually disconenxcted
like split into two
so bascially, (-infity, -n)?
connected sets do not have to be closed/open right?
yep, but obviously you'd need at least some other elements in the set since otherwise the intersection is empty
yes
i thnk ill go with the set $S_n = {(x,y): x \neq 0, y \in (-\infty,-n) }$
LXDL
thus the intersection will be everything except the y axis
if i wanted to prove that each $S_n$ is connected, should i use contradiction?
LXDL
or would just going with the nomral defn be better
its disconnected
x!=0
oh yeah
maybe i change the set to $S_n = {(x,y): (x \neq 0 \text{ OR } y \notin [-n, \infty) }$?
LXDL
ye connected
i didnt read anything before this so idk if u need other properties
@velvet coral Has your question been resolved?
ye ive ben trying to show its connected but am having trouble
id show path connected
how would i do that? it seems to be quite messy/ many paths
@velvet coral Has your question been resolved?
drawing the set helps u see the path
u will see two cases, the points lie on opposite sides of x=0 or they lie on the same side
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It's my physics que can anyone answer it?
Que in which wire phrase or netural is electric switch connected?
If not then I will colse
@short depot Has your question been resolved?
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Correct. Now all you need are your justifications.
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is th5e second integral wrong, shouldnt' the cubic be negative or smthn
it will automatically be negative because uhh that's how the function works
just plot the integral graph you'll see that it is negative in that interval
is it becuase of the abs value
just lemme plot the integral gimme a minute
and you'd see
the integral function is
<0 for x=1 to x=4
so you won't have to worry about what values would be -ive or +ive
since the integral will automatically give you -ive and +ive values
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Area and Perimeter of this Algebra Tiles
<@&286206848099549185>
any info at all?
whats x? can you screenshot the whole problem
uhm, it should be pretty obvious with the area
three whole x^2 squares and three x^2/2 half squares
Idk but people said it 14 but I am confused on how.
Perimeter.
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it's 7...
Only look at B.
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an easier method would be
making an x * x square
then subtracting or adding to fit the shape
that will give you an easier time with area and perimeter
I don't get how they got 14cm as the perimeter.
btw because of how projections work, this will have perimeter equal to x*x square + twice the length of the small boxes
dw the answer is 7
i think
because of how projections and perimeters work, this will have perimeter equal to a rectangle of dimensions 5*
so the perimeter becomes 2 * 5x + 2 * 2x
= 7 * 2x
which is just 7
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i'm preparing for an integration bee in which we get a "cheat sheet" of sorts, one of the facts on this sheet is (a), but I just kinda don't get it
What is y in this situation? where does this come from? is this like a special case of (b)? How can I use this for definite vs. indefinite integrals?
thanks to whoever helps me :)
$\int f^{-1}(y), \mathrm{d}y = \int x, \mathrm{d}\left(f(x)\right) = \int x, f'(x), \mathrm{d}x$
Mqnic_
IBP: $\int x, f'(x), \mathrm{d}x = x, f(x) - \int f(x), \mathrm{d}x$
Mqnic_
^ (a)
(b) observe such diagram for the geometric interpretation of (a) under suitable intervals
I see, do you have an example in which we can apply (a)?
i have literally never seen this used in my life
figured
and i have seen a fair number of integration bees
b is important, however
know how to recognize tricky sums related to of inverse functions
yw
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I know I should be using a theorems based on primes to answer these.
No clue where to start from... or which one is an easier answer.
@upper schooner Is it not based on primes? Or am I tripping cause this was given to us on the chapter about primes?
You don't need prime factorisation to show the statement true, at least
I'm presuming that maybe they might use that somewhere else, though it would be quite weird imo if they're expecting you to show it from prime factorisation
I'll go down the chapter this is in and see if we don't need to. I'm actually kinda of confused this chapter not gonna lie.
Awwww 
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What's the probability of rolling a sum of 12 with 4 six-sided dices
I just gotten to a+x+b+z+c+y+d+q = 12 and minimum value is 1 for a,b,c,d so it's x+y+z+q = 8
So js using stars and bars I gotten 165 total combinations
But this includes the fact that a,b,c or d can be greater then 6 so the max value is uh 9
Idk how do I calculate how many like restricted combinations are there
I was thinking of doing js if a = 9 so b+c+d = 3 = 5C2 which is 30 but after calculating it it's wrong compare to the awnser sheet
what are all these letters?

@compact hawk Has your question been resolved?
the count can be rawdogged like this

probably easier than trying some stars and bars shit cause the corrections for upper bounds on dice scores might get quite nightmarish
π
also btw http://anydice.com/
π
Also doesn't this take a long time
Like in the test I get 2 minutes per question
And this is the easy part of the test
i didn't time myself
took me just about 2 mins in all
How would you even calculate it like this then π cus I can't think of a way without spending like 5-10mins
No like how did you like calculate this quickly
which part
finding the patterns?
finding how many permutations each one gives?
adding up the permutation counts?
Yes
About the ss u sent
How did u calculate it quickly like that
Cus like for me I always js used stars and bars to calculate these types of questions so I got no idea how u did it like that quicjly
so just to be clear: you understand the "pattern" column, but want to know how i did the "permutations" column specifically, correct?
in that case: in each pattern, i calculated the number of rearrangements of n objects with repetition
eg for the pattern 6321 all four dice are distinct so it's gonna give 4! permutations, but the pattern 5331 identifies the 2 threes so 4!/2! = 12 permutations, and 4422 identifies two pairs this way therefore 4!/(2!*2!) = 6
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hi
i need help
hi i need help on this problem ive been working on: Consider the first 30 terms of the following integer sequence:
1,4,7,12,20,32,44,60,81,108,135,168,208,256,304,360,425,500,575,660,756,864,972,1092,1225,1372,1519,1680,1856,2048
I need to determine a pattern or formula for the
n-th term. I have already checked the OEIS database and attempted polynomial interpolation, but I was unsuccessful.
I found the pattern lies in the second difference, but its a periodic sequence plus a polynomial of somesort.
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I need to prove this using induction
I've don the base case
And now I'm proving this
But somehow the next step became this
(I'm looking at the answer book)
I don't understand how 1+(k+1)x became (1+x)(1+x)^k
wait no
No its the left part that become this
Ok
See
Take your original inequality
And multiply by 1+x both sides
Don't flip inequality cuz 1+x >0
But why multiply 1+x on both sides?
Cuz x >=0
To have the lhs as you want
Now you need to show that rhs >= 1+(k+1)x
Yeah
But I didn't multiply the lhs?
I need to prove for k+1
so the k+1 didn't come from a multiplication of (1+x)
It does for lhs here
Wdym
but we just want to transform the expression of k to something in the form of k+1?
Like I thought we need to replace all ks with k+1
Oh yeah or either starting from k+1 assomption and use the fast that its true at n=k to prove your induction
ohhhhhh thanks
so we just transform the expression
no substituing right?
Yeah transform what you have to what you want OR transform what you want with what you have to end something true
You're welcome
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james josh and judy are sight seeing in Egypt, James (A) is south of the great pyramid of giza, josh (C) is west of the pyramid, whilst judy (B) is in between them on the line AC. the angles of elevation from A, B and C to the top of the pyramid are 23 degrees 24 degrees and 25 degrees respectively, find the bearing of the great pyramid of giza from where judy is standing to the nearest degree
i was told by the person who gave me this question that the answer nice is ||North 3 degrees east|| however when i did it i got ||92.772|| so i think i added ||90 degrees|| somewhere
my working out was:
||let g be the base of the pyramid, let t be the top, let theta be the bearing from B to g, let h be the height of the pyramid aka gt tan24=h/GB GB=h/tan24 tan23=h/AG AG=h/tan23 tan25=h/CG CG=h/tan25 tan<CAG=CG/GA = (h/tan25)/(h/tan23) = tan(23)/tan(25) thus <CAG = arctan(tan23/tan25), angle <BGA = theta (alternate angle on parrel lines, B to its north and GA is north to south, hard to explain) sin<GBA/GA = sin<GAC/GB sin<GBA/(h/tan23) = sin<GAC/(h/tan24) tan23 x sin<GBA/h = tan24 x sin<GAC/h tan23 x sin<GBA = tan24 x sin<GAC sin<GBA=sin<GAC x tan24/tan23 <GBA = arcsin(sin<GAC x tan24/tan23) theta = 180-GAB-GBA (angles in triangle add up to 180) theta = 180 - (arctan(tan23/tan25)) - arcsin(sin(arctan(tan23/tan25)) x tan24/tan23) but that makes theta 92.7 when the answer is meant to be 3 degrees, i cant find my mistake T-T||
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If vectors of some set A are a linear combination of vectors in B then B is necessarily found in A
@light hazel Has your question been resolved?
What do you mean? What two sets are you talking about?
But the first isn't a vector space
Or you mean the vector space spanned by (0,1) and (1, 0)?
I donβt think so. The closest thing would be that W = span{(1,1)} is a subspace of V = span({(1,0), (0,1)})
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Could anyone guide me on this question? I'm not so sure how to appraoch 1.a
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well the most obvious method is to just find R and R'(in terms of m) and equate
but that will take too long
its supposed to be solved in under 5min
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just looking at 'CE = EP'
does that mean the vectors are the same
or just their magnitudes?
just the magnitudes
if it was referring that the vectors were equal, then they wouldve added the arrows on CE and EP
and them being on a straight line makes their directions the same right?
so overall they are the same vectors when u combine them two facts?
yes, as a matter of fact
u have a theorem stating if E is the midpoint of [CP] then vector CE = vector EP
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I need help
Make an integral that shows B - A
i got this
why is the answer
the one that is c and b
the given answer is this?
this
i wrote cb integral - the ab integral
but i dont understand
why there is a minus on cb
integral
because its below the x axis
oh
this will be a negative number
the area is positive (we think of areas as positive) so if we want to talk about the positive area we need to multiply that
by -1
this is trippy
alr
thanks
so everytime its under the x axis
i put a minus
sign
if u want the area ya
oh
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Yes
i got the answer tnku bro
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$\Omega \subset \mathbb{R}^n$ is an open set, $A, B$ differentiable functions,
$A : \Omega \rightarrow M_{mn}(\mathbb{R})$,
$B : \Omega \rightarrow M_{nk}(\mathbb{R})$,
$u : \Omega \rightarrow \mathbb{R}^n$.
$\forall x \in \Omega, V \in T_x\mathbb{R}^n$, we define $V(A), V(u)$ as the differential of A and u along the vector field V.
I try to see if $V(AB)=V(A)B(x) +A(x)V(B)$.
Need some help please. One of first things I'd like to understand is, how does $V(A)$ even look like?
I know if $V=\Sigma_{i=1}^nV_i\partial_i, u=(u_1(t), ... u_n(t))$, then $V(u)=\Sigma_{i=1}^nV_i\partial_i(u_i(t))$. How would it work on a matrix though?
HI
Wild123
Formatted the question.
I think I have an idea. I'll reopen later if I get lost.
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Why donβt you just write V \in T\Omega
I didn't know the command π
Ohh I was copying it as I had it
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y=3x^3-6 hello I am supposed to determine if this is one to one
do you know what the definition of one-to-one is
nah
π€
I think It means if two numbers add up to the same number or something
every value input value only has one unique output value
no two input values have the same output value
why are you doing homework before knowing the material
no
a function f is one-to-one if f(a) = f(b) implies a = b
for example if
f(x) = x^2
f(-1) = 1
but f(1) = 1
Since two input values give rise to the SAME output value, the function is not 1 - 1
cause I need to and this isn't in the posted notes
doubt it
I could send you the notes
you have
$$f(x) = 3x^3 - 6$$
Edmund Cloudsley
set f(x) to a and b. If this implies that a = b, the function is 1 to 1
3a^3 - 6 = 3b^3 - 6
use this to show a = b
thus establishing f is injective/one-to-one
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you could also watch this video
to strengthen your understanding
uhh kinda confused on the a to b thing is 3x^3 a and -6 b or ?
bruh
read what weβre saying to understand it not to figure out what you should copy on your paper
$$f(a) = 3a^3 - 6 = f(b) = 3b^3 - 6$$
Edmund Cloudsley
@obsidian plank as @misty crest mentioned earlier, please do go through the material first
it would be hard to solve this question if you don't know what a 1-1, many-1 and 1-many mapping is
the last two have to be some red coat shit bro wtf is 1-many
dude I am just trying to understand what you guys are saying bro what's the attitude for you can't expect me to know something the first time you say something and have me not ask questions
like the graph of y = +-\sqrt{x}
1 input value maps to many output values
,w plot y = +- \sqrt{x}
so not a function?
if an input value maps to multiple outputs then itβs not a function
you didnβt even read my definition
^
do you understand what that definition entails
an equivalent formulation (the contrapositive) is if two input values a and b are such that a β b then f(a) β f(b) for a one-to-one function
trust me dude I am trying to understand this if I wanted to just get it done I would just use chatgpt and cheat on this shit but im not
I think I got it now though
essentially it just means distinct inputs yield distinct outputs
thank you
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how did the max become 3? wouldn't it just be e
well its kind of self-referential
the thing you are trying to work out in the first place is the range of what it could be
$\max\qty{e^z}$ for $0\le z\le 1$ is just $e^1=e$.
mathisfun
Since e^x is increasing for all real x.
they also arent claiming that the max equals 3
they only claim that its bounded by 3
so would i be able to out down 2.8 instead
Sure. Anything greater than e (reasonably, of course)
thank you so much bro
the question is whether you know at this point what e is
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Hi, this is a picture of the truss problem I have been working on. I need to solve forthe forces in the members listed in the top right (BF, AF, and FG). The thing that is tripping me up is that both the supports are pins and therefore have horizontal reactions. I cannot solve for these reactions no matter how hard I try. Any guidance would be much appreciated, thank you.
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why did they word it like this?
yeah
ohh u are right
i just checked the pdf textbook
what does In mean?
Do you know about logarithms?
ln is natural log, its the same as saying log base e, where e is euler's number.
some basic proofs are that $\ln(e^x)=x$, $\ln(e)=1$, and $\ln1=0$.
im here to save the day
hi
Krish
um
the only time ive heard of eulers number is when u differentiate e^x u get e^x
yes
ln also is all based around eulers number.
is there a graph 4 it
there is a graph
,w graph ln(x)
$\ln$ tells you what power you need to raise $e$ to in order to get a certain number.
Krish
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struggling on number 3, have i gone about it correctly?
@junior heron Has your question been resolved?
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when you did the u sub, you haven't substituted the du
thank you
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Ik its prolly basic, but which areas do we substruct. Is it area under the linear - area under the parabola or smthn else
for part 2 btw
the top curve - the bottom curve
on the domain
of interest
so the linear - the parabola, yes
but tbh, the order does not matter. if u get a negative answer, just absolute value it and u get the right answer
though
i was thinking
the area under the linear given there is no parabola will just be infinity
@wispy oyster could u solve it as well since i need to double check my answers coz there is no solutions available
I have gotten 9/2
she means area between two curves
!showwork
Show your work, and if possible, explain where you are stuck.
after u've finished ur work u, u can self-check by
- wolfram alpha
- other CAS, say https://integral-calculator.com
Solve definite and indefinite integrals (antiderivatives) using this free online calculator. Step-by-step solution and graphs included!
,w int x-4-(x^2-4x), x=1..4
@supple trench would the theory behind be correct
your working / answer is correct, yes
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I'm confused of ChatGPT's answer about the vector matrix multiplication. I run it on my ide and I got a different solution than ChatGPT told me. It's even the same code. How is that possible? π
!noai
chatgpt is nonsense
it doesn't actually do the calculation, it just finds the sentence that looks the most likely to follow
So is it just like the problem with the number of r's in the word strawberry, where ChatGPT thinks that it's 2, instead of 3?
yup
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Hey, first a bit of context (sorry its so long). I am working on an implementation of the bin packing problem (you have x items of a certain size, how do you pack them optimally in the least amount of bins of size y) but a small tweak: there are multiple possible bin sizes.
I have an implementation which is working and I'm happy with for now, but I now want to add progress reporting to the calculation. The algorithm itself is a simple branch and bound for now. I had the idea I could a crude upper bound for the total amount of possible (or impossible) packings: (bin_sizes + items)! / (bin_sizes - 1)!. Reasoning behind it is: first item you have bin_sizes choices (you put the item in a new bin of one of those sizes), next item has bin_sizes + 1 choices (add them to the existing bin or create a new one)... and so on. I know this also includes impossible packings since it does not take into account capacity of the bins and it always assumes all choices up until now have been the creation of new bins.
Now I want to also keep track of the explored packings, since the ratio would then ideally be the progress of the calculation.
When I reach a leaf node, I have a complete packing: increment one to the explored space.
When I bound a branch I intend to also very aggressively update the explored space to counteract the upper bound which is too large. I update with (bin_sizes + bins_in_current_packing + items_left - 1)! / (bin_sizes + bins_in_current_packing)!
I'm now wondering if this is a valid way of tracking the progress. I actually know it isn't since my implementation of this fails (never reaches 1% progress, or my implementation is wrong). Intuitively it seems to me like it should work, if I envision the decision tree of the total packings, then my updates just prune the subtrees. But I might be wrong in that it gets all the subtrees, which is where my intuition ends lol... I'm kind of stuck now on how to fix this, or if there's a better way to track the progress.
@rain solar Has your question been resolved?
@rain solar Has your question been resolved?
Hey <@&286206848099549185> can anyone help me? π
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Prove that Ax=lambda x eigenvalue is real if A=A*
\begin{gather*}
A^* = A \rightarrow a_{i,j}=\overline a_{j,i} \\
Ax = \lambda x \\
A = \lambda x \cdot x^{-1} \\
A = \lambda I \rightarrow a_{i,j}=\lambda \in \mathbb{R} \\
\end{gather*}
is this correct?

