#help-23
1 messages · Page 129 of 1
do you need help with anything else?
i just started this exercise
so idk now
if i have i will chat here or to you
if its okay
ok, np
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How am i supposed to solve this?
My book said some stuff about. put your right hand in ??????????????????????????
anyways, my book didn't teach this
the right hand rule 
arrange your thumb, index and middle fingers like this, vaguely in the shape of an orthogonal triad
thumb = a
index = b
middle = a × b
in your case specifically, thumb = v, index = B and thus middle = F
(if q > 0)
Proposition: Ann has at least one hand
proposition: Ann has at least one right hand
WHAT
what?
are we sure you didn't use a cadaver
do you have a right hand or are you an amputee
you can't really draw this.
or is ti like this
this looks vaguely phallic.
anyway like
in these drawings
treat the x axis as going left to right
y as bottom to top
and z as directly towards you
yes
for q>0
do them all for q>0
then the ones for q<0 are just opposites of those
these drawings are from a fever dream
this is REALLY phallic.
NO THEYRE NOT
You're mind is just in the wrong plae
It's literally a hand
a very artistic rendition thereof.
i'm dead

wait
cross products
aren't like
$$ \vec{a} \cross \vec{b} \neq \vec{b} \cross \vec{a}$$
One person
so
(1) and (2) aren't the same?
So
$$ V_z > 0$$
so that means
$$ B_x > 0$$ as well
so
?
One person
<@&286206848099549185>
$$\vec{a} \cross \vec{b} = (a_x \vec{i} + a_y \vec{j}) (b_x \vec{i} + b_y \vec{j})$$
One person
One Person
$$\vec{i} \vec{j} = \vec{k}$$
$$\vec{j}\vec{i} = -\vec{k}$$
One person
I think I can help
One person
.close
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Does anyone have a better explanation for this problem?
Everything that I have found just says
" Use the answer to solve the problem "
Do i just like
create a list
and see if any of the vectors I have will put me on teh target square
and if there are none
I extend the list by 1
like
The vectors in the red being the list of positions i can reach with just two vectors added together
I would then check if its equal and if its not add another variable to one side
then try to solve for that variable using the vectors I have already
if you didnt have the "cant step on" condition itd be easy no ?
and if none can be used I create another list of vectors that use three vectors added together instead of just two
you could just take 2 displacements and make them your basis vectors then find out the coordinates of the target vector in terms of your basis
sorry 3 displacements*
now you can just repeat that until you find the combination that works
(maximum 4 repeats)
thatd be a technical way to solve it
im pretty sure if you solve it like that by ignoring the "cant step on" condition you can just rearrange the terms to avoid the point
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Hello! This is my first time asking for help here. I have a math degree from 10 years ago so my calculus skills are very rusty. I have attached my work and wrote my entire thought process so far to this question. Mostly, I want to make sure the next direction(s) I am trying to take make sense? If not, what should I consider instead? Thank you!!
@slate gale Has your question been resolved?
I haven't looked terribly closely at the particular function you have but in general a good idea is to solve for when the gradient function equals zero
and the gradient function is a function that consists of the partial derivatives
so essentially you want both of the partial derivatives to equal zero and that should give you a system of equations
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Why is it that when we solve for (x^2 -1 ) and get -1 the limit is approaching -1 from the positive side
x^2 - 1 is always bigger than or equal to -1
so we must be approaching from the positive side
but aren't we finding the limit as x approaches 0 which technically will be less than -1
because say we use -0.0001^2 - 1 with 0.0001 being x
x^2 is always positive or zero, x^2 - 1 will never be less than -1
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qingfengmingyue
question?
Ok firstly, I'm going to be a bit picky on notation
So its about how you use that mod n
The way you've written it is uh... a bit like how a CS student would
,,2+3\equiv 0\pmod 5
oops
now the problem is
you cant really use this notation I suppose?
because this notation kindof assumes youve proven its a group and whatnot
im just tryna clear that up in my mind but yeah
In any case, I don't like this notatoin.
For 10a, I probably would've gone contradiction/contrapositive approach
Suppose x * y is outside Z_n
Then show its not the least non-negative remainder
Oh wait shit i just realised
Ok yeah, that notation is 'ok' given how they defined the operation in the question 😒 (ew)
but thats not how modulo arithmetic is usually introduced in group theory
😒 😒 😒
Which parts of group theory have you done up to this point. Ill have a look at b
i still don't feel like you've proven commutativity/assoc properties properly
this is the approach and what I would rely on to do it
thats alrightt hen
xy = yx = qn + r
wouldve been commutativity
justifying its the same r
associativity is slightly more pain.
=================
moving onto b
Am finding it hard to read - you happy about the identity element you found?
its just 1 I hope
yh I think you should rewrite it making that clear
Your proof should just prove 1 is the identity
oh nvm u put the associativity proof first no wonder i was confused
but yeah still using this
x . 1 = 1 . x = x = 0n + x
associativity comes from part 10a, no need to restate it.
sure.
qingfengmingyue
So bezout's won't make much sense til you figure what variable needs to be what
ax + by = 1
I would try writing out the final result you're after and maybe it'll be clear.
again, use this
what must x^-1 satisfy
still related to this
x' * x = 1 yes
using that operation *
but how to express in the standard operations in Z
You need this
what is x' * x
sorry
what is x * y
how did we define it
the result is r
where q is taken as big as possible
keeping r the smallest
ok?
r is the least non-neg rem
so now write that for x, x'
(im using x' in plaintext as easier, but obvs dont in handwriting)
xy = qn + r -> x * y = r
its not necessarily 0n
for example integers mod 5
2 and 3 are inverses
2 . 3 = 1 . 5 + 1 -> 2 * 3 = 1
yeh
x' . x = k . n + 1 for some k in Z
-> x' * x = 1
now do some rearranging
lets write x' as y for now so tis easier
xy = kn + 1
rearrange it so it looks like bezout (wont be same letters)
right
xy + (-k)n = 1
We've done a backwards proof basically
Now you need to start with bezout, and work forwards
to show what x^-1 must be.
but you have all the steps
yes
if its associative in some superset
it must also be in a subset
you can see this with quantifiers
(forall a, b, c in X) something
implies
(forall a, b, c in subset of X) something
=====
ig u can justify this with a quick one-liner but yeah
basically
but not really
you've miswrote it
So we defined our operation in a pretty convoluted way
x * y is the least non-negative remainder when xy is divided by n
y * x is the least non-negative remainder when yx is divided by n
but xy = yx
therefore x * y = y * x
==========
You could also define:
x * y is the smallest possible non-negative r of the integer tuples (k, r) which solve xy = kn + r
I think this works???
but in any case, this definition is by no means nice
well you see in all these definitions and proofs I'm writing, I've avoided saying xy mod n
Its convoluted if we want to be precise with our words
this has right idea but isnt precise because it misses details about k, r
these 2 lines were the most clear for commutativity
But you will need the algebra for associativity
oh im high maybe lemme reread
This still works, because its impossible to get remainder 0
with the set 1, 2, 3, ..., p-1
under division by p
And that actually needs to be part of your proof in b
To show this operation is well defined on U_p
====================================
x * y is the least non-negative remainder when xy is divided by n
y * z is the least non-negative remainder when yz is divided by n
(x * y) * z is...
x * (y * z) is...
Yeah actually this is the best way, I just realised.
maybe
actually maybe not nvm - u defo need the algebra
=========================
x * y is the least non-negative a of the integer tuples (p, a) which solve xy = pn + a
y * z is the least non-negative b of the integer tuples (q, b) which solve yz = qn + b
(x * y) * z is the least non-negative c of the integer tuples (s, c) which solve az = sn + c
x * (y * z) is the least non-negative d of the integer tuples (t, d) which solve xb = tn + d
xy = pn + a -> xy - pn = a
then substitute that back in.
is the approach
bruh this is painful 😒
uhhhhhhhhh
So x(yz-qn)=xyz-xqn=tn+d
Thats half of it
what about the other substitution
xy = pn + a -> xy - pn = a
yz = qn + b -> yz - qn = b
you use both of these to show (x * y) * z = x * (y * z)
😵💫 i need 5-10 mins lmao
You get these equations after substituting. Can you rearrange them so that they're both xyz = ???
(xy - pn)z = sn + c
x(yz - qn) = tn + d
good good
a lot of letters
but you can carefully read the formulations we had
to figure out how to justify c = d
without referring to mod anything 
(s+xp)n+c
(t+qb)n+d
essentially u gotta show s+xp = t+qb
to show that, u gotta show this
The way to think of it is --- they will be equal, because you are 'able to make them equal'
xp and qb will be some random numbers. You are able to pick s and t to be anything
to make c and d as small as possible
^
maybe there was some simpler way to do all of this, but yeah, idk honestly. That definition sucks 🙄
not really.....
smallest possible while taking into account s and t are integers
ngl im half lost in proof as well at this stage sigh
But basically yeah you do have to justify c = d
and the original question did ask you to do it using associativity property in Z
😢
The other thing I'm gonna say at this point is that this proof is not terribly important.
In terms of revising/your course
like dw too much about it
The important part was bezout
which we did
modular arithmetic is usually defined through group quotients
which is much nicer to use
i think u need to do that as well technically
luckily this ones quick
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Show that if $G = (V,E)$ is a simple graph with $n$ vertices and more than $\ds \binom{n-1}2$ edges than $G$ is connected
Been grinding my gears for this one
Really can't figure out what the hell I'm supposed to do
pigeonhole principle?
How exactly?
not sure about the (n-1) instead of (n) but if it was n you could just say that you have n vertices and you need to choose 2 per edge
so nC2 edges in a graph will obviously have one edge at least per choice of two vertices
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tan(-5π/6) = tan(-pi + pi/6) = tan(-180+30) = tan(-150) =tan(210) = tan(270-210) = tan(60) = sqrt 3 I am trying to find the exact value of this and dont know where i went wrong please help
p.s I checked and the answer is meant to be 1/sqrt3
@vale elbow Has your question been resolved?
<@&286206848099549185>
Try expanding tan(15-90) in terms of $\frac{sin}{cos}$ and then expand sin and cos expressions using known indentities.
NZzska
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Can someone help me with this?
How can I answer in exact value when sin(π/8) doesn't give an exact value?
there's a certain double angle identity to be used here
(cos(x))^2?
I'm confused 😢
i suppose you haven't been taught the identity but you're supposed to use cos2x=1-2sin^2x
x here is pi/8
so all of this turns into cos(2*pi/8) or cos pi/4 which is 1/sqrt(2)
Then it would become cos(π/4)!
that's right
yaaaay
<@&286206848099549185>
What was the command for trig identities?
!rocket
!help
Please read #❓how-to-get-help
@upbeat ridge Has your question been resolved?
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here, i think the most valuable knowledge to have is where 5pi/3 is on the unit circle. In other words, Q1, Q2, Q3 or Q4. I cannot visualize it however, easily, where 5pi/ is on the unit circle. I can only think if it was 6*pi/3, it wouldve been 3pi, which is out of the unit circle lol. Any advice
6pi/3 is 2pi not 3pi
and 3pi isnt out of the unit circle it is simply at the same point as 1pi
oh yeah lol
my bad too quick to say that
but still
is there any good way to visualize where 5pi/3 is on the unit circle
besides memorization
like i know the values up until pi over 2 in my head, just where to place the rest
pi/3 is one sixth of the way around the unit circle
so 5pi/3 is five-sixths
it'll land in the fourth quadrant
nice, i like that
and every value pi/x , we can see the progress as 1/2x
so pi/3 = 1/6 progress
andthus pi*5/3 = 5/6 progress
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This answer of mine does not feel right. I feel like it doesn't take into consideration if one of the 10s is a spade. Thoughts?
<@&286206848099549185>
what's your thought process?
Sorry, I was missing this part
there are 6 cards that are spades. there are 4 cards that are 10s. there are 21 remaining cards. i need 2 spades, 1 ten, and 2 other cards to make up 5 cards in a hand
@dapper venture
yeah you didn't considerate the case when you have a spade 10
try breaking it to 2 cases
case 1 with spade 10 and case 2 without spade 10
In that case... C(3,1) C(1,1) C(22,3) plus C(3,2) C(6,1) C(21,2) seems to be right maybe?
3?
explanation: the first is the case where i need 1 ten that isn't a spade, a 10 of spades, and 3 other cards. the second is where i get 2 tens (not spades), a spade, and 2 other cards
which 3 are you questioning?
in the second part, shound the C(6,1) actaully be C(5,1) because I dont want one of the spades considered? (the ten of spades)
should be C(5,1) instead of C(6,1)
are we referring to the same thing?
no
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I'm working with matrixes yeah, and I've been told to add multiple matrixes/subtract matrixes which do not have the same dimensions
Do I just say "Not possible?"
Yes
I haven't seen those for years, I don't remember how to do that actually
Oh
it's quite a procedure haha
check out this youtube video, about 7 mins only
Thanks to all of you who support me on Patreon. You da real mvps! $1 per month helps!! :) https://www.patreon.com/patrickjmt !! Please consider supporting me on Patreon! Be a Patron of Mathematics! https://www.patreon.com/patrickjmt?ty=h
Finding the Inverse of a 3 x 3 Matrix using Determinants and Cofactors - Example 1. Besides using row red...
Yes, I know but I don't remember the steps lol
This video should be enough to illustrate the steps required!
This says finding the inverse is it the same thing with cofactors and adjoint?
Yes, to compute the inverse, you need the adjoint
And to compute the adjoint, you need the cofactors
Interesting
The three are related, inverse adjoint cofactor
Can I leave this open till i'm done?
7 mins only
Sure!
$$A^{-1}=\frac{Adj(A)}{det(A)} \hspace{2cm} det(A)=|A| \ne 0$$
$$With: , Adj(A)=[ , Cof(A) ,]^{T}$$
LUNA
Quick question, if I'm multiplying 2 matrices where the columns of matrix A is not the same as the rows of Matrix B can I still multiply?
No D:
Yeees
$$A(m , \times , n) \hspace{2cm} B(p , \times , s)$$
$$You , can , multiply , A , by , B , only , when , n=p$$
$$And , the , resulting , matrix , will , be , (m , \times , s)$$
LUNA
So
I have Matrix A(1x1) and Matrix B(1x3)
Does that mean I can only multiply A x B
but not B x A
Exactly!
Matrices multiplication is not commutative
it's not like real numbers, 2 x 3 or 3 x 2 same thing
Okay okay nice, just like cross product of vectors?
Yes
But cross product is a bit nicer because it is almost commutative, it's only off by a sign when you swap the two vectors (we say it is anticommutative)
What
the length of rows of first matrix and the length of columns of second matrix must be equal
Across the row, down the column
I know lol, i was telling him that matrices multiplication is not commutative like real numbers multiplication
So this
These were not dimensions, but real numbers
:p
was supporting your argument
with a clear image
Okay so each number takes another
What is the case when one number in a row takes the entire column?
When it's a 3x1 matrix and 1x3?
Yes that's an example
No, a 3x3 matrix
If it was 1x3 times 3x1 then yes it would result in a scalar (a.k.a. a 1x1 matrix)
[1]
[2] x [1 2 3]
[3]
Answer would be a 3x3
No, 3 x 3
That's if it's 1x3 and 3x1
Your result needs to be a 3 x 4 amtrix in the end (just to check the answer in case you need)
I know iot will be 3x4 I just don't know how to arrange it
I've multiplied all numbers in the first row by the numbers in the first column
Continue the process you began
Do I go to the second row and second column?
No, you first have to multiply the first row with all the columns. Having done that, you can go on with the second row
oh wow
So I start from 3 again
3x5
and 5x1
Wait no
I always have to add?
The row times columns would be the element in the new matrix. Because you know it's a 3 x 4, the first row by the second column would result in element (1, 2) of the new matrix
That's how matrix multiplication works
Do you notice how the multiplication of the first row in the first matrix, times the first column in the second matrix results in the element (1, 1) in the new matrix?
Same logic for the rest, if you look at that image, first row by the second column is element (1, 2) in the new matrix, etc
I think I understand this and the one you posted dldh06
So when I finish one roqw by column
I add it up
and the do the column with the same row
https://youtube.com/watch?v=vzt9c7iWPxs
If it helps watch this
This precalculus video tutorial provides a basic introduction into multiplying matrices. It explains how to tell if you can multiply two matrices together and how to determine the order of the new matrix. The order of the new matrix is based on the rows of the first matrix and the number of columns in the second matrix. To multiply two matric...
when you have free time, you can also explore something a little advanced but more fun
Strassen Algorithm (You won't use it for now)
I have Symbolab premium but for some reason I can't solve Matrix questions with it
I can only use the examples
I like using this site, www.matrixcalc.org
Do i have to add?
No
Why don't I have to add for this scenario
Because it's one element times the other
It's just 2 * 3
There's no more elements in the column to sum
https://matrixcalc.org/
That site btw is good to use
It shows the work
Interesting
thanks
So it's always
One row multiplies an entire column
Then you add
Then you repeat it w the remaining columns
Yeah
@sage shore
wassup
The vdieo you gave me I've completed it and got the inverse
How do I know which ones are the co factors or adjoint
Should I send a pic?
The cofactor matrix is the first matrix you compute
The one which resulted from the 9 little determinants with signs next to them
That's the cofactor matrix
The Adjoint matrix is its transpose
Keep diagonal of cofactor matrix, and swap others
Noice
But why don't you name them, to be clear in your answer sheets
$$A^{-1}=\frac{Adj(A)}{det(A)} \hspace{2cm} det(A)=|A| \ne 0$$
$$With: , Adj(A)=[ , Cof(A) ,]^{T}$$
LUNA
Okay
I don't klnow why this is under Business Administration
I have to simplify the fractions yeah? @sage shore
As you wish, or as your teacher does..
Some would divide all the entries by 60 and simplify
All of them I suppose
Some (including me) would leave it as (1/60) Adj(A)
Well this has been fun
Somehow finding the inverse is easier than multiplication I think
How do I know which numbers to switch when I'm transposing the Cof(R)?
No way!
The guy has shown you in the video
Yeah, diagonal stays the same
And the "mirrors" numbers get swapped
kind of mirror the numbers which are not in the diagonal
Also, transposing a matrix is making its rows its columns, and its columns its rows
Yeah, this is more common
I see
When I was finding the cofactors and I found those mini determinants, why didn't I put the big number outside
Like when you're normally finding the detemrinant there's a number outside no?
Because those are not exactly determinants
More like the minors
They are called minors
oh I see
So when finding minors for the co-factors I do not have to put the number outside
And when you add the alternating sign, they become called cofactors
Yes, no need!
yes, alternating
What happens if the determinant of a matrix is 0?
Then the matrix does not have an inverse
I'm not trying to do the inverse right now
I'm trying to do Cramer's Rule
To find the values
of 3 variable equations
Then Cramer's rule cannot be applied
Interesting
Because either there is no solution
Or infinity of solutions
Not one unique solution that you can find using Cramer's rule
Waiiit, nooo
Cramer's rule is not applicable when D=0
Not Dx1 and Dx2...
Dx1, Dx2... can be 0, it's okay
Here, D=-12, so it's okay to proceed
Oh i See
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I don't understand how the answer is p = 0.002. Also, I'm unsure what table to use
@pine dove Has your question been resolved?
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it's fine🥰
im stuck and i think i did it wrong lol
What happened between lines 2 and 3
idk i tried changing the denominators to add them up
but they didnt work

i just noticed a mistake💀
sry
lol
lemme try again
ok nvm i still cant get it @pseudo scroll
Apparently it has decent solutions
how😭
how is cotx = cosecx - 1 
ik i just said i made a mistake
oh ok
but even after that i still cant solve it🤡
lemme try
yeah well, just just cot to cos/sin
and multiply whole equation by sinx
and then you can easily factorise the equation

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back. i need some help for question 2
!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
2
What have you done?
Wait but, you sent #3 no?
yeah
its the same question
i was just doing other questions before it
hence 25
12.3
I do see a small mistake in your answer here
its not my answer
its a step but
when you brought the -2 inside the log to the exponent you forgot the -
i felt something was wrong so i didnt continue
oh
lemme look
so is the quadratic part supposed to happen?
depends on the way you're doing it, but in the end, it will give the same answer
I recommend you don't factor the polynomial though
And also, you replaced y with x, but didn't replace x with y, so you have x'es on both sides which is not what you're supposed to do
oh my bad
bad*
so (y+2)(y+2)
wait
factoring it was a waste of time
i just got what i had before
a step 3, where its x-2 = log-2(y-1)^2
can i just distribute the -2?
i thought i couldnt, which is why i factored it
but when i factored it, i ended up getting what i wouldve gotten if i just distributed the 2
Why is there a - inside the log?
as in the (x-1)?
no, as in -2()
$y = -2\log(2(x-1)) + 2$
imTypθ
There is no -2 inside the log?
oh that
wait a minute...
the whole thing is wrong now
because -2log2(x-1) = log2(x-1)^-2
negative exponent
yes
so what now?
i guess i should apply the negative exponent property
imTypθ
Yeah, you can distribute the exponent
sure. Be careful because the 2 is inside the exponent too
oh
so if theres an exponent and log like: clog_a(b)^n, then the exponent would apply to the entire log including c right?
just to clarify
so the right hand side would be 1/(4(y-1))^2 right?
looks right
Just do your usual algebra to isolate y.
what? Why? I think you can
after the step i mentioned earlier, i did:
10^x-2 = (4y-4)^2
but since i didnt know how id get y on top, i had to bring it to the left hand side
(4y-4)^2) 10^x-2 = 1
wait
ill try to solve this further
wait, i cant
and this is looking nothing like the answer on the sheet
so i cant do it
You can...
I know exactly why you have a different answer, I'm just waiting for you to get there
What step are you currently on?
step 7 ^
$10^{x-2} = \frac{1}{[2(y-1)]^2}$
imTypθ
That's where I left of. What did you do next?
10^x-2 = 1/(4(y-1))^2
(4y-4)^2) 10^x-2 = 1
i dont know what to do next
the only thing i can think of is divide both sides by 10^x-2
well that's a good start
but how am i going to get y by itself?
$4(y-1)^2 = \frac{1}{10^{x-2}}$
imTypθ
Do you not see the way to isolate y?
Also, you can simplify the RHS so that it looks more like your answer key
what you do to one side you do to the other
But yes, dividing by 4 is the way to go
However, I'd consider doing this first
is it 10^-(x-2)?
(y-1)^2 = 10^-(x-2)/4
$(y-1)^2 = \frac{10^{-(x-2)}}{4}$
imTypθ
You're almost there
ill try something
ok nevermind
the only way im thinking of to get rid of the square is to do a sqroot
but the answer has no sqroot
It has one, but it's kind of hidden. How else can you represent the square root?
^1/2
There you go!
y-1 = (10^-(x-2)/4)^1/2
y = (10^-(x-2)/4)^1/2 + 1
but thats still nowhere close to the answer unfortunately
it is, you just don't see it :) What can you do when you have a fraction raised to an exponent?
you multiply it by that power?
so if the fraction is raised to 2, you multiply it by itself
but this is a half exponent so
wait a minute
nevermind. i was thinking to use the exponent property of (a^m)^n = a^m+n
m in this case being -(x-2)
well, you will have to use that, but you confused two properties
$(a^b)^c = a^{b\cdot c}$
imTypθ
But what I was talking to you about was this property
oh my bad
$\left(\frac{a}{b}\right)^c = \frac{a^c}{b^c}$
imTypθ
thatd make it 10^-(x-2)^1/2 / 4^1/2)
right. And i am sure you can evaluate the denominator
yeah. itd be 2
correct. As for the numerator, you can use this property
alright
So, does the answer look more like your answer key now?
kinda, but
the exponent for the numerator,
since its raised to the half power,
-(x-2)^1/2 = -(-0.5x-1)?
yeah. Multiplying by 1/2 = dividing by 2
yeah
however, your answer key doesn't do it, it just leaves the /2 there
Wait a minute
I think I know how to get the answer now
Instead of doing (0.5x + 1) [since there’s a negative outside the bracket]
i can just do 1/2x + 1
careful distributing the negative
imTypθ
I think that's what you have?
i actually didnt have it like that. i shouldve wrote it down
i think the exponent should be (-1/2x + 1) then?
Sure, but I don't why you don't just leave it at that?
You can distribute the 1/2 in if you really want to, but it's not mandatory
oh
well, its kind of because of this answer, but i think it probably has the same value as this
it does have the same value. Just distribute the negative and you will see
but when i distributed the half, i got (-1/2x + 1)
i think ill just stick with this answer, to be honest
I said distribute the negative, not the half. See how the answer key keeps the /2 outside the brackets?
oh
sorry if that wasn't clear
ohh i think i get it now
:D
since its raised to the half, you can just write it as 1/2(10^-(x-2)
then when you distribute the negative
itd be (-x+2) in the exponent
so the exponent, if rearranged, would be (2-x)
this was one heck of an inverse function...
thanks for the help
no worries! Those will become easier with practice :)
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is this correct here?
looks good to me
any part youre worried about specifically or confused about?
answers all look correct
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Каква е вероятността Б да се случи, в предположение, че А не се е случило и Б може да се случи само ако А не се е случило?
English:
We have two events A and B. B can only happen if A did not.
P(A) = 0.2
P(B) = 0.1
P(B | not A) = ?
брат, това е английски сървър, имаш ли екранната снимка на въпроса?
Знам, но знам, че може да има и човек, който да ми помогне. Въпросът не е от някаква задача, а мой собствен.
добре, проблемът с въпроса ви е, че трябва да посочите вероятностите of a и b да се случат или не, преди да можем да го изчислим вместо вас
Вероятността може да е всякаква, но нека кажем, че на А е 0.2, а на Б е 0.1
Просто бих искал да знам правилната формула
ще оставя въпроса ви на английски, за да може някой да помогне
Няма нужда, аз говоря английски също
He is asking what is the probability B will happen assuming that A did not happen and B can only happen if A did not happen?
<@&286206848099549185>
о, не знаех
@blissful phoenix Has your question been resolved?
@blissful phoenix Has your question been resolved?
How did you calculate it? What's the formula?
Ако A не се е случило, тогава вероятността B да се случи може да се определи чрез намиране на условната вероятност за B при условие, че A не се е случило. Това може да бъде представено като P(B | не A). Тъй като B може да се случи само ако A не се е случило, можем да приемем, че P(B | не A) = 1, което означава, че ако A не се е случило, тогава B със сигурност ще се случи.
English version:
If A did not happen, then the probability of B happening can be determined by finding the conditional probability of B given that A did not happen. This can be represented as P(B | not A).
Since B can only happen if A did not happen, we can assume that P(B | not A) = 1, meaning that if A did not happen, then B is certain to happen.
That doesn't sound right. The probabilities of A and B I gave are 0.2 and 0.1.
Does 1 not mean that it will always happen?
I feel it is 0.8
Oops sorry I didn't use the probabilities
If the probability of A is 0.2 and the probability of B is 0.1, and it is assumed that B can only happen if A did not happen, then we need to calculate the probability of B given that A did not happen.
If A did not happen, this means that A's complement (not A) happened. The probability of not A happening is 1 - 0.2 = 0.8.
Therefore, the probability of B happening given that A did not happen is 0.1.
P(B | not A) = 0.1
I feel it's also 0.8
Since the probability of A not happening= three probably the B happening
Still doesn't sound right. You didn't say why this is the case:
Therefore, the probability of B happening given that A did not happen is 0.1.
I don't think B is supposed to be assigned a probability
Since the probability of a not happening is already B
I said it was 0.1 because you gave me 0.1
The probability of not A happening is 1 - 0.2 = 0.8.
You said this yourself. P(B) = 0.1
TheHermit
That's ok. I appreciate the effort but can we leave this to someone who knows more about probabilities.
Jangler
With the given information, we know that $P(B \cap A) = 0$ has to hold (as B can't happen if A happens)
Jangler
Use $P(B) = P(B \cap \bar{A}) + P(B \cap A)$ and you get an expression for your wanted probability
Jangler
So since $P(B \cap \bar{A}) = P(B)$ can we say $P(B | \bar{A}) = \frac{P(B)}{P(\bar{A})} \implies P(B | \bar{A}) = \frac{0.1}{1-0.2} = \frac{0.1}{0.8} = 0.125$
Velizar
Exactly
Ok, nice. So I checked the wiki page on conditional probability and can see where your first formula came from and the one after it also makes sense but where did the third one($P(B) = P(B \cap \bar{A}) + P(B \cap A)$) come from?
Velizar
$B = (B \cap A) \cup (B \cap \hat{A})$ \
$(B \cap A)$ and $(B \cap \hat{A})$ are disjoint, so the probability of their union is equal to the sum of the probability of both sets. (Third Kolmogorov axiom)
Jangler
@blissful phoenix Has your question been resolved?
Makes sense but how do we know the equality $P(B) = P(B \cap \bar{A}) \cup P(B \cap A)$ is true? We know $P(B \cap A) = 0$ but how can $P(B) = P(B \cap \bar{A}) = P(B) * P(\bar{A}) = 0.1 * (1 - 0.2) = 0.1 * 0.8 = 0.08$ be true? It seems necessary but weird to assume $P(\bar{A}) = 1$
What mistake am I making here?
Velizar
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if both of the function's domain is different why is the graph same ?
where is not same
?
cscx is never zero
Well, if you know what csc means
1/csc(x) is equivalent to sin(x)
yea but the domain of it is different than that of sinx
No, the domain is all reals
sinx's domain is R
1/cscx's domain is R-npi
nope, it is R
x's domain is R, 1/1/x's domain is also R
that is really what you are doing here
writing 1/(1/sin(x))
this is just sin(x)
it has denom 1
it is defined over all of R
of csc(x)
yes
but not of 1/csc(x)
Just like this
the domain of 1/x
is R-0
the domain of 1/(1/x) ?
all of R
it is just x
no
yes
Shouldn’t that still be R\0
1/(1/0) is still undefined
disagree
if you cant calculate certain parts of an expression then how should it be defined there
Not in the domain
1/(1/x) is not equal to x
^^
it is undefined at x=0
Yes
so both of the domains are different right ?
oh well then forget I said anything brist0l
you can continuously extend 1/(1/x) to x
but its a different function
with different domain
The graph looks the same because you’re missing points
And Desmos can’t show you the points
Cos there are infinitely many points close to the ones missing
what does it mean " missing points" ??
Missing as in they aren’t being graphed
so i need to zoom in to find those ?
You have to glide over it to see the hole
yea lol
That’s the one weakness of desmos tbh
ayo
