#help-27
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∮Ē.dĀ = Qₑₙ꜀/ε₀
$\mu = e^{\int -\frac{1}{x} \dd{x}} = \frac{1}{x}$
∮Ē.dĀ = Qₑₙ꜀/ε₀
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dont worry im also stupid af
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ez af question but here:
this is not an equation. there is nothing to solve.
well then it should say simplify.
ok, so disregarding your friends' incorrect step
do you have any other progress so far
yeah i do
show
Are you saying your friends gave this to you?
yeah we review for an upcoming test it's not part of anything though
Tell them next time they write down "solve" there better be an equal sign
yes 🙏
Ann
but then what was your final thing
or like
your final answer
cause the way you wrote the cancellation is a bit sus
or maybe the last line is cut off?
1/x^2(1-x)
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how do i find number of solution of x^2 = 2^x
without graphical approach
probably intermediate value theorem
what is that
that is not taught to us
so i guess ill have to do it using graphs itself
or maybe just do substitution method
thx anyway
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need help solving this problem:
Battleship Puzzle
You have a 10 × 10 grid.
You can place mines on certain squares to prevent a ship from being placed.
Question 1:
What is the minimum number of mines needed to prevent any ship from being placed if ships have the following shape (a horizontal line of 5 squares)?
🟦🟦🟦🟦🟦
Question 2:
Same question for the following shapes (or other shapes of your choice):
🟦
🟦🟦🟦🟦
🟦
🟦🟦🟦
🟦
(A "+" shape)
and
🟦🟦🟦
🟦
🟦
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where did the first inequality come from?
kheer257
u sub and then bound by largest value of f
and then factored that out of the integral
what exactly are we subbing?
ahh I see
it's kinda dumb, but z = z(t)
[ \begin{aligned}
\abs{\int_{\gamma}f(z) \dd{z}} &= \abs{\int_a^b f(z(t))z'(t)\dd{t}}\
&\le \int_a^b \abs{f(z(t))}\abs{z'(t)} \dd{t} \
&\le \sup_{t\in [a,b]} \abs{f(z(t))}\cdot\int_a^b \abs{z'(t)}\dd{t} \
&= \sup_{z\in\gamma} \abs{f(z)}\cdot\operatorname{length}(\gamma)
\end{aligned} ]
kheer257
I don't understand why they added an inequality sign at the end though
is $\sup_{t\in [a,b]}\abs{f(z(t))}$ not necessarily equal to $\sup_{z\in\gamma}\abs{f(z)}$?
kheer257
now that I think about it, how do you even define a supremum on a curve?
just call g = f(z) and now you have sup(g) over [a,b]
and the bottom sup is just equal to the top sup by definition
@feral agate this is sometimes called the ML-inequality, if you want to google it
riemann is correct, but im just giving you a name for it
thank you very much! I wasn't sure what name to search this by
right and z smoothly parameterizes gamma
i'm not sure what is confusing you
nothing actually
thank you for your help
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do you know the definition of x-intercept
yes it’s a point that intersects the x axis
that's true, yeah. so if you have a function y=f(x), in general, not just for this problem, how do you find the x-intercepts of f?
also called the roots of f
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Think about when will the graph intercept the x axis
What does it mean for a line to touch the x axis
I have to show my work with out using or showing a graph.
so like through a method ig
Idk how to do that
Like if I got out graphing paper I could find it but without graphing it I’m stuck
Oh, then desmos.com should help. Also, it'll prolly help to watch youtube video on tracing graph of a quadratic function
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Can someone check my work and lmk if I’m on the right track or not
I think I’m getting it somewhat
My work seems a bit messy and untrue
@vagrant shard Has your question been resolved?
Is there a chance that x=-41 isnt right?
The 4 is correct but c/a which is x1.x2 should equal to - 1
Which in your case it is - 164
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Thanks for ur help!
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ok ik what a unit vector is and ik how to do it
but im confused about c)
because the magnitude that I get for c) is 15.62
but why is the textbook using the same magnitude for a) in the answerkey
isnt the unit vector different since now its u + v so magnitude is different
textbook answer
a unit vector is a vector of magnitude 1
yup
if you multiply a vector by a scalar, then its magnitude is multiplied that amount
so if you were to divide by its original magnitude, the new vector would have to have a magnitude of 1
ya ik
i know how to form it
but im confused why my answer isnt right
yuhh
so isnt the unit vector 1/sqrt244 ( u + v)
(sqrt244 = 15.62, the magnitude)
I think they probably messed up 
omg ok
😞
because this is what the texbook wrote..
But 2sqrt21 is the magnitude for u-v...
oh well
Thanks chartbit

Yea and I agree with what you have 
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i need help passing the math section of the ged and getting a better score on my asvab. how do you retain information well? whats the best way to study? please help, everything just goes in one ear and out the other nothing really sticks. am i cooked?
There's a crayon joke to be made here.
But honestly its just repetition. The asvab isn't particularly tricky or unique, its just a fairly significant amount of material being tested. Don't try to memorize any topic, go through it monday, then wednesday, then friday, and so on. You'll manage to internalize it after enough iterations.
is there any particular trick to studying like i heard chewing gum and scribbling on a paper while reading or some shit like that
idk twin im just tryna become an academic weapon
i just quit smoking weed 3 days ago maybe my brain fog is too bad rn i dont really know 😭
Nah. No need to overcomplicate it. You literally just need to bash your head at as many questions as possible over a long time period and you'll ace it.
Make sure to get step-by-step solutions to the ones you can't do/get wrong though.
But yeah no magic tricks unfort
ive been working with chat gpt as like a sort of math teacher and its been helping i guess your right about it just being repetition. i gotta write down a schedule and stick with it because i kinda js study whenever i gotta be more specific with it
Yeah. Be a bit careful with using chatgpt since llms can get wrong answers while sounding confident, but it should be mostly fine for the asvab. Better if you find practice sets/textbooks etc. I guarentee that if you study for 2-ish hours a day for at least a month or two you'll score high enough to be the nuke guy
which apparently requires a really high score (?)
damn i didn't know chatgpt was buggy like that
but yeah i was thinking of getting textbooks and stuff
ik you can probably find them for free online
aightjamin twin i dont got anymore stuff to ask
ill lock in on studying every other day for 2 hours though
thanks g
,close
fuck
how u close it 😭
.close
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Hello!
the integral of 1/x dx = lnx + c
wait nevermind it clicked
as i was writing the question
😄
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how do I solve this? I specifically need more help with part B. I haven’t learned derivatives yet and must utilize the IROC formula but i’m unsure how to start.
Did you try completing the square
How would I do that?
,tex .cts
riemann
ty I think i got it from here
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How do you approach a question when the bases aren’t the same?
Like this?
yeah!
Now I apply the addition formula and switch to exponential form?
Is that the way to do it or am I missing smth?
you're overcomplicating things
Alright how should I solve this then?
it's just basic algebra from here
clear the denominators
multiply the equation through by log(2)*log(3)
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help
have question about how to write answer
for (a) i got (-1,-7),(3,6)
don’t know if that’s how to write it
they want the interval between the x values
when we talk about a function's behavior on or over an interval or other set, we talk about stuff on its domain
would i only state the x values then?
for decreasing would i write (-inf,-1)
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how do i show that a particular point is the only limit point of a set E
this is my function
whats your defn of limit point?
Point s.t. its every neighborhood has nonempty intersection with E?
,rccw
I'd try taking any limit point of E and proving that it equals 1
my professor hadn’t done an example for a particular number before i didn’t know how to do it
Let's start with a simpler case then. Can you prove that any x < 1 is not a limit point of E?
tbh i don’t know how to these proofs work at all wouldn’t know how to prove that
Okay, what does it mean if something is not a limit point?
Refer to the definition
it wouldn’t have a anything in the set of its delta neighbour hood excluding itself
Yeah, to be more exact, there would exist such a neighbourhood
because there is no the neighborhood
there are plenty possible neighborhoods
Now returning to this, can you find a neighborhood for e.g. x = 0 which doesnt have anything in common with E?
for my example if i choose x =3/2 and a small delta it will only include itself
Yep, that's right and that's also the core of the argument
to make the argument exactly right, you'd only need to choose the right delta
I'd split this up to 2 cases, x < 1 and x > 1
the x < 1 case is simpler, so let's start with that
what delta can you pick for x = 0?
What delta can you pick for x = 1/2?
what delta can you pick for x = 0.99?
What delta can you pick for general x < 1?
(i just gtg quickly do sth, ill be back in few mins)
for x= 0 i can pick a delta that is less than 1 because no value of 1 + 1/n is between 1 and 2
Exactly
in general for 1 i just need to pick a delta such that x + delta is less than 1?
Yep
okay
one way to do that is just pick delta = 1 - x for x < 1
hmm okay makes sense
now for x > 1
this one is a bit more complicated
you have the right intuition that by choosing a small enough delta for e.g. x = 3/2, you can ensure that the only point of E inside the neighborhood is x itself
now the question is just how small does the delta have to be
the delta we choose is because of left of the point if that makes sense
we are closer to the left points
That's not always true
if you had x = 1.499 you'd be closer to 3/2 than to 4/3
luckily for us, we can just determine the distance between both the point on left and the point on right and just pick the smaller one for our delta
We just need to find the "point on left" for our x
there is a theorem which says that every nonempty subset of naturals has a least element
if we consider the set of all ns, such that 1 + 1/n < x, then we should be able to pick the least n0, which will result in the point of E which is right to the left of x
the point on the left would then just be 1 + 1/n0
1 + 1/(n0 + 1) must then be >= x (since it cant be smaller)
so it's either x itself, or to the right of it
can you finish the argument by choosing the right delta now?
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Guys how do I solve
Ended up getting these 2 linear equations but didn’t work out
Can someone show me the right one
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@frigid torrent Has your question been resolved?
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I'm currently working on understanding modal analysis, my starting point is a sdof system to understand the eigenvalue problem. As far as I've seen so far the eigenvalue Lambda was defined as: Lambda = omega², with omega as the angular frequency and omega² = m/k, both of which can be derived from the statements in the screenshot.
What I don't get is the middle part, which states that solving mlambda²+k=0 for Lambda gives you Lambda1,2 = iomega, which in my understanding gives you Lambda1,2 = omega (not squared).
What am I missing here?
What I don't get is the middle part, which states that solving mlambda²+k=0 for Lambda gives you Lambda1,2 = i*omega, which in my understanding gives you Lambda1,2 = omega (not squared).
what squared part are you talking about from the picture ? I don't see what you're talking about
but anyway, you're solving m L^2 + k = 0 for L, i.e. L^2 = -k/m
k and m are positive most certainly so -k/m is negative
Sorry, not a native, I'll try to explain better.
L^2 = something negative, the solution has to be imaginary/a complex number
yeah that checks out, this is not the part I'm looking for.
I'm looking at the solution for L:
It's either L = omega² or L = omega, whether imaginary or not.
I have learned so far that L = omega squared, which makes sense, given that L² = -k/m and k/m = omega²
Why is the omega not squared in the middle part?
k/m = omega²
what's sqrt(k/m) then ?
omega (not squared)
Ok, I understand where I took a wrong turn in this context.
Still, I have learned that L = omega² when doing modal analysis
Is that only true for dampened systems with one or more degrees of freedom?
can you post their explanation around that formula ? (gonna be in german I guess)
@graceful oyster Has your question been resolved?
I'm trying to find something useful. I originally got it from an online lesson about modal analysis for 3 dof system (bridge). But there it was just described as a given. Within that example it makes sense and replicating that with my FEM software gave me the right values as well.
Thats a screenshot from the given video. There he only states that Lambda = omega ²
Also another book that I have describes the eigenvalue problem as (K-omega²M)[Eigen vector] = 0 but also for a 2dof system
Sorry that I don't have more to tell you. It's kind of my problem rn
I have found this in english, also speaking about mdof systems.
yeah I'm out of my depth here, sounds like they're talking about a different type of eigenvalue
you could try asking in #modeling if no one else comes here
also ping helpers @graceful oyster
Alright, thanks for your time and effort regardless
<@&286206848099549185>
To specify for people willing to look into this:
In my understanding the eigenvalue Lambda is equal to the square of the angular frequency omega: L = omega²
for the sdof system without dampening I found that Lambda seems to equal omega (not squared) It's also not specifically described an eigenvalue (problem) in the book I'm working with. I'm confused as to why there seem to be two seperate connections between Lambda and omega
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@graceful oyster Has your question been resolved?
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Is this correct?
It's ||not|| incorrect, ||non-||sadly.
-# Never let them know your next move.
.close
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How to do this correctly ?
Answer is 0, but how to get it
As simple as possible probably
for x between 75 + 15 and 75 + 135
Is there a way by solving something?
plotting is as simple as possible
What does that mean ?
,w plot cos(x)
Once we have [90:210] what then ?
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Is the distance formula for radius the same as it is for diameter?
And..is it derived from the "equation of a circle"?
What's that formula supposed to be used for anyway?
What is the "distance formula for radius"?
which formula exactly are you referring to
Uhh I'm not quite sure but it's just the distance formula.
I just specified it because i was unsure
Can you provide any additional context?
Can you formulate the distance formula for us?
Maybe the original problem
It's not a question problem, I just want to clear my concepts.
A square bee square sea square?
This formula gives you the distance between two points (x1, y1) and (x2, y2)
Yes
So where do your radius and diameter come from
So the same i guess
radius and diameter relate to a circle
You can use it with a circle
but what it does is gives you distance of two points
I don't know i read somewhere that it's (x-h)² + (y-k)² instead for radius
That's for offsetting the origin
Dude
So it's essentially the same thing just using the actual variables for the points as they are?
That seems to be derived from the circle equation.
What's it supposed to entail?
If we call the center of a circle (x0, y0) and the circle has radius r, then for every point (x, y) on the circle it holds that the distance between (x, y) and (x0, y0) is r.
If you write this algebraically, according to the formula you described, then you get that
sqrt( (x - x0)^2 + (y - y0)^2 ) = r
which is more commonly stated as
(x - x0)^2 + (y - y0)^2 = r^2
https://www.desmos.com/calculator/jckfamgeem
Play around with this desmos graph (use sliders for a, b and r) to get some intuition on the topic
Thanks
The last equation is called the equation of a circle, because every point on the circle described by r and (x0, y0) satisfies the equation
and conversely every point satisfied by the equation lies on the circle
How'd the r get squared at the end
Because of the pythagoras' theorem
But r isn't a point on the circle just the distance
Yes
Oh yeah
My bad didn't see the sqrt
Yeah that is what i was exactly asking
Alr, do you understand it now?
No i still don't understand what the equation of a circle is supposed to be used for
I mean for a few(a lot) things but, primarily for drawing a circle?
Like if you ever have a graph which needs a circle you use this equation
Hmm
How exactly
Like, coding or?
Programming could be one use for it, ye
If a geometric object is of the form some expression of x y z = 0, then we can find its normal vector at any point very easily using multivariable calculus. If we have a temperature distribution T(x, y, z) in space, then we can restrict that temperature distribution to a sphere x^2 + y^2 + z^2 = 1, and find the biggest temperature on the sphere by using multivariable calculus
I can't code but how could i use it except solving problems from a maths book
That depends really, which field do you wish to pursue IRL
Is that 0 or just a variable
0
Like anything that i could do as a layman i guess to get a better understanding of it
that is actually zero because mathematicians find it aesthetically pleasing (and some other reasons too.)
For instance the equation of a circle can be turned into that form if you write it as
(x - x0)^2 + (y - y0)^2 - r^2 = 0
If you just wanna get a better understanding of the equation, play around in desmos
That's prolly the easiest way to get used to it, as for how that equation comes to be
Do you know the definition of a circle in math?
How can i find the intersections of 2 circles?
!occupied
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Mb
Hi
Yeah i get it, y-axis, x-axis & circle big/small
mhm
?
Are x y z in "x y z = 0" all multiplied or..?
No, he's just saying some expression involving the variables x, y and z
Uhh a 2D shape? With all points equidistant from each other from a fixed point.
Is 360° etc
Yes, Good job
well each other not so much
but from the center
Formally speaking
A circle is the path traced by a point travelling in a 2 dimensional space, such that it remains at a fixed distance from some fixed point.
I don't understand the entire msg tbh, don't know most of the things being talked about or why there are specially 3 variables x,y, & z
Yea, that would make sense considering you're just learning about 2d equations still, don't worry, it'll make sense in future
Do you understand this?
I could've written F(x, y, z) = 0 for some function F but some people are scared of functions so I occasionally try to avoid them, perhaps causing more confusion in the process. Sorry about that
Yeah
Kind of like a planet but not quite
Ok, so now think about it in terms of this definition
You are so motivating hiten thanks
Our everyday geometry is always three dimensional, and even if it's two dimensional, it's occasionally a good idea to embed a two dimensional object into three dimensional space. Of course three variables is somewhat arbitrary in the sense that these ideas do generalize nicely to higher dimensions as well
If a point is in a two dimensional plane, then we measure two things about it, it's vertical distance from the origin, (y), and it's horizontal distance(x) from origin,
Yeah
What do you mean by
Embed a two dimensional object into three dimensional space ?
then, let's fix a point, and let's call it $P_C = (x_C, y_C)$ do you know what this notation means?
@autumn girder
A two dimensional object can rest on the xy-plane, even if we have a z axis. This can occasionally be helpful if we have a special technique that only makes sense in three dimensions, but we still wanna try to apply it to a two dimensional object
No but I'm guessing P stands for point & C = centre?
Yes
$x_C$ is the horizontal distance of the center point from the origin, also called it's x co-ordinate and same applies for $y_C$
@autumn girder
$P_C = point of centre$ ?
👾
Yep, it's the central point
of the circle
Does this make sense so far?
Sounds like a regional convention, I've never seen that before
So basically h & k ?
We can get to conventions later
Legit just made it up lol
Where do you guys get the roles from
At the end of the day it doesn't matter how you write things down, the mathematics is still nonetheless the same. For me (x0, y0) makes more sense as the center than (h, k), but obviously you can call your center (å, ö) if you want to
I thought you were talking about a cult
that said, yes they're h & k in the formula
Why's it called h,k?
I don't know. I wouldn't use h and k
No reason except one guy woke up one day and decided to call it that
Oh
now we say that every point on the circle must be at some fixed distance (radius) from this center
i.e. if some point $P$ is on the circle then $distance(P, P_C) = r$
@autumn girder
So far we have just mathematically written down the statement of definition
I hope there is no confusion thus far?
Yeah none
Um the formula
Yep, the distance formula
do you understand how that works?
or should we go into that for a bit
and then come back here
Well
?
I wanted to know about the equation for a circle not the distance formula
I mean from here the next step is just the equation of circle
Yeah let's move on
$distance(P, P_C) = distance\left((x, y), (x_C, y_C)\right)$, because recall that every point is defined with two properties, it's x and y co-ordinates
@autumn girder
$distance((x, y), (x_C, y_C)) = \sqrt{(x - x_C)^2 + (y - y_C)^2}$
@autumn girder
This is just the distance formula by definition
and from here, we put it equal to r, as we derived from the definition of circle a few steps ago
Yeah
$r = \sqrt{(x - x_C)^2 + (y - y_C)^2}$
@autumn girder
and there you go, there you have your equation
What's it supposed to be used for tho? also a last step left lol
Also could i see how to get the formula, step-by-step
Circle
What more steps do you want, we went from definition to formula, which step did you feel was missing?
Yeah this but where does the - minus & square root get added from
No there's circle one at the end too
It simplifies to it i guess
I'm just curious why the - & square root get added
They get added when you use the distance formula from here
How tho
I don't get how it gets added
Ok, let's go into distance formula then
Would you agree that the distance between P1 and P2 here is gonna be equal to the length of the line joining P1 and P2?
Well...yes
Ok good
A lot was added here but does it make sense?
Thanks for doing this
NP
Yes
You should already have some intuition where we're going with this
y-axis (0,a)
x-axis(a,0)
Yeah
Here I color coded it a bit so that it's easier to see and added more stuff, does this makes sense too?
@dusty fox
Ok cool
So now you see the right angle triangle formed by the purple, blue and orange lines?
Yes
What would the length of purple line be, in terms of the orange and blue line?
Hint: ||Recall, Pythagoras' theorem||
Oh Pythagorean,
H² = P² + B²
Sum of P2P3 & P1P3 ?
Sorry for keeping you busy for so long, tbh I will revisit this sometime later, getting a bit late.
You could propose a time sometime later to continue from here, how's that sound?
@autumn girder
Would you agree?
That's fine by me but you already have the answer at this point
Yes
Oh yeah nvm
p = the length of line between P1P3
$90^{\circ}$
@autumn girder
Do i..? 🥲
So when ?
h is the distance of P1P2, right?
I gotta adios for now
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You're welcome
.
@autumn girder
@autumn girder
@autumn girder
Yea, and now this is an exercise for you
Calculate p and b from the graph
You can do it on your own
Later if you don't wanna do it rn
Hint: ||Look at the grid lines which have been drawn for your convinience||
The length of p and b
They won't be h
Yeah half of H
No
Huh
Did you look at the hint?
Well, it happens lol
Ok I'll do it later
thanks again, but when will u be available
You can just post the question here
There are other helpers and they'll also be willing to help
so dw
Well yes, will do it later
Can't manage to keep this open
Alr, for now since your original question has been solved
please close this thread with .close
But..the homework
?
U just gave for me to solve
You can post it here for people to check or, ask if you have any doubts
don't worry, you'll be fine
If you want you can dm me too
Well
I'm asking cause i don't want to be waiting after sending it.
And if i know when you'll be available then getting it done quicker would be easy
Unfortunately, due to the current circumstances I am in, I can't give you a fixed time
So your best bet will be to use the help channels
when you need them
Under any circumstances, I'll close this channel for now.
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I need some help generating the transition matrix for this problem... I have an answer I'm just not sure if its right. I would love to compare work with someone. Thanks!
that takes a nontrivial amount of work to do
but maybe someone will be up to the task
You should probably try to network with the students who are actually taking that course with you
I generated a 13x13 matrix with this... Im "pretty" sure its right though
But Q, and I, in the F=(I-Q)^-1
What would those be if i only have 1 absorbing state in my 13x13
Because i need to make a fundamental transition matrix from it
You can cheat it a bit by not including the bottoms of ladders and the tops of chutes, since you can't land on those squares
So we're down to an 8x8
Thats what I was wondering about tbh. I included them in my matrix, but would that change the outcome?
Like in my matrix, since 3 goes to 7 with a ladder, rows 3 and 7 are the exact same in my matrix
same with chutes
The only absorbing state should be the end im pretty sure, so Q would be all others in a 12x12 and I would be a 12x12 identity matrix?
Heres my fundamental transition matrix, what exactly do these numbers mean?
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if we have something like z = sqrt(4-x^2-y^2) and we were to graph the domain (x^2+y^2<=4) and range (0<=z<=4) together on one graph, what would this represent?
It would look like a hemisphere.
$$x^2 + y^2 + z^2 = 2^2$$
@drifting sinew
When you take the square root of both sides, you find that z cannot be negative, so the sphere turns into a hemisphere
if i graph the domain and range at the same time, what would I get?
i know S is a hemisphere
Try to figure it out yourself; I don't want to do too much of the work for you.
I can try to give you a hint if you're not sure.
would I get a cylinder?
But we already established the graph is a hemisphere.
@bleak arrow Has your question been resolved?
That is indeed your domain
In that, the whole upper hemisphere, z = sqrt(2² - x² - y²), having radius 2, is enclosed in (it's a hollow hemisphere note that)
the domain is x^2+y^2<=4, right? but if i were to graph the domain and the range together, what would you call this in math?
Nothing really like this is still math. You just restricted your domain R³ to the cylinder
if u have a curve instead of a surface, u can represent the curve by domain + range, right? if u have something like:
intersection of z = sqrt(4-x^2-y^2) and z = 1, u get for the domain: x^2+y^2=3, and for the range: z = 1, u can write the equation of the curve as "x^2+y^2=3 at z = 1"
is there something similar to surfaces?
Err note that this is not really a domain technically because z is not defined for the circular strip 2<x²+y²<4. I don't know a better word for this, but if it were a disk of radius 2 centred at 0, that is your domain
Like for a semicircle with radius r, the domain is [-r,r] (which can be restricted), for a hemisphere it's x²+y²≤r² (which can be restricted)
For semi-circle, your "workspace" is R² but is not your domain
So even in hemisphere, you're "working in" R³ but that isn't your domain
The intersection is a level curve that you get -- a circle with radius sqrt(3)
isn't the domain x^2+y^2=3 and the range z = 1?
is it just a coincidence that the equation of the curve is x^2+y^2=3 at z = 1
When you say z = sqrt(4-x²-y²), your
domain is the natural domain where the whole function z is defined in (without any restrictions) which is x²+y²≤4 and your range is the z values [0,2]
In other words, z is a mapping from D(0,2) -> [0,2] where D(0,2) denotes disk of radius 2 centred at 0
When you show both of them in R³, you get the surface -- hemisphere
The cylinder is not technically your domain, the disk is
for the example of the curve, is it always like this? the equation of the curve is the domain + the range?
Yes when you graph the curve both input values (domain) and output values (range) are there, plotted as points on the curve you get
show what?
So when you plot a point on the hemisphere (x,y,z), (x,y) is a part of your domain (the disk) and z is a part of your range
The domain you're working in and the range you get
so the domain for the surface is the disk x^2+y^2<=4, and the range is the region 0<z<2
0≤z≤2 yeah
if i graph them together I get the surface?
Graph them together as in you're plotting z = sqrt(4-x²-y²)
how?
.
If you plot the disk separately that's different
If you graph domain separately, you get disk
Graphing the range separately gives you a line segment over [0,2] on z-axis
Plotting the curve z=sqrt(4-x²-y²) gives you the hemisphere
I never used 3D desmos but just typing in z=sqrt(4-x²-y²) should work
ok thanks
You're welcome. Have a great day
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I'm getting -10/3
Got a=1/2 by solving the inequalities
So the parabola is y²=2x
Then slope is -beta/alpha no?
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Hello
Next Tuesday I have my Algebra 1 class final
I was wondering if anybody had anywhere I could find a solid review to go over this material
And also our final will go over a portion of midpoints and distance
Oh thanks
But I also need like an algebra 1 full course review
Thanks brother 🫡
I need hlp
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why sqrt(2n)*q^n -> 0
as n-> inf
where -1<q<1 a constant?
not an argument i can use
in calc
Why not?
rigorous class
ah.
have we tried taking limits
how exactly
since -1<q<1 we can write it in this format
;(
We know 1/q will be some positive number that is not a fraction (since |q|<1 implies that it is such)
For q in the rationals
q in R will be a bit difficult but we can still get there
Just show that an exponential equation a^x with |a|>1 grows faster than sqrt(x) and you're all set
;(
Sorry if this is a bit too much info
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is this valid for all discrete distributions?
they say its for discrete distributions with non negative support, but they all kinda do. you cant put negative numbers into NB or Hyp. its just that some supports dont include 0 and now idk what to do with it
it's valid for distributions of RVs that only take natural-number values.
including 0 in the support is fine too as it kinda inherently contributes nothing to the expectation
like
0 * p(0) is just 0
what if its for NB where support starts at r?
that's also fine, the probabilities for points less than r will just be zero
do i have to pay attention to the lower limit of the summation?
as in...?
do i ever have to change x=0 into sth else
no, you don't have to
but it is sometimes a good idea to prune known-zero terms from your sum if you see any.
but don't overblow the importance of that.
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Is it f(X) + f(X-1) ?
oh hol up
wait a min
aight think in terms of difference of 2 consecutive squares
see a pattern
?
f(20) + f(19) = 20^2
=> f(20) = 20^2 - f(19)
f(21) + f(20) = 21^2
=> f(21) = 21^2 - (20^2 - f(19)) = 21^2 - 20^2 + f(19)
f(22) + f(21) = 22^2
f(22) = 22^2 - (21^2 - 20^2 + f(19)
f(23) = 23^2 - 22^2 + 21^2 - 20^2 + f(19)
You can see the pattern.
ohh yeah
bro we r suppose to make people suffer and realise the answer tho
but isnt that kind of an ugly pattern
nope
cause i need to find the remainder right
It's an alternating sum.
yeah
It's not hard to find f(94) itself I guess.
wait is 10^2-9^2
are u kidding
there would be so many squares
(n+1)^2 - n^2 = (2n+1)
think in terms of difference of 2 squares
yeah so ill need to do this for many terms right?
yeah but then u get 94+93+92+91+.......+21+20+f(19)
which ig u can do
if u know wat to do
huh yes i can do this sum but im a bit confused to how u got it
It should be + and - tho
deez
how did 94^2-93^2+92^2 so on become 94+93+92...?
This mf trollin
me?
92^2-91^2
94^2 - 93^2 = (94 + 93)
Not u
no way
moye moye
ohhh ok got it
oh ok so i can use this to find f(94) directly
and then divide by 1000
thanks man
np
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wait
.reopen
✅
yeah?
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np
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I’ve been trying to get the derivative of this and have done several retries, the strategy I’m employing is taking the natural log on both sides to bring down the exponent of e. Any guidance informing me where I went wrong or how to get this derivative would be greatly appreciated. Thank you
,rccw
Do you know implicit derivatives?
It’s been a few weeks so I’m rusty
Get the derivative and when you derive y dy/dx becomes a coefficient and you isolate that
Afaik
Yeah I’ve been trying to but all the answers I’m getting are different than what google says the answer is
Can I send some other attempts, I feel like there’s something I’m missing
Or maybe does the ln to bring down the exponent strategy not apply here? That’s my best guess
It can work, but there is a much simpler way to do this
$\exp(a-b) = \frac{\exp(a)}{\exp(b)}$
@autumn girder
Where $\exp(x) = e^x$
@autumn girder
So the exponent since it has subtraction, can be put into a quotient form basically? Am I understanding that right?
Yes
So how would I rewrite that in this case? 5e^(2x/y)?
Isn't it 5e^(2x - y)?
Yes
I think im misunderstanding the formula my bad
$5e^{2x - y} = \frac{5e^{2x}}{e^y}$
@autumn girder
Got it thank you
And then just do quotient rule and chain rule
Going to try it out and send a pic one sec
Ok
Uh... you should've taken e^y to the LHS and brought x to the rhs
so that you'd have all the y stuff on one side and all the x stuff on one side
This should still work, don't get me wrong
but let me check
Oh I see, but like shouldn’t it work out either way, can’t you isolate dx/dy after getting the derivative? (ok cool yes)
I did notice I moved a term and forgot to make it positive cause it was negative
Otherwise though not sure
Where did 2 go from, $5 \cdot e^{2x} \cdot 2 \cdot e^y$
@autumn girder
You’re asking like where I got the 2 from? In the quotient rule section? Could you circle it maybe?
No, I'm asking where did it go in the next step?
Oh I see yeah I forgot to make it 10e
Thank you, amending that, otherwise how does it look
Thank you I appreciate your help
Though if you can, try seperating variables and then use implicit differentiation
this will give you an answer faster
and less error prone
Yeah going to redo the problem and do it in that method
Alr, cool
Got a final at the end of this week so gonna do a lot of review, wish me luck and best of luck to you and all your stuff
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Can anyone help me with the scalar product of [-28,0,18]*[-1,0,3] I keep getting 82 when I try it but that's wrong
are you sure you are wrong
I think whatever answer sheet you are using is actually wrong though, (-28)*(-1) + 18*3 is indeed 82
if by scalar product you mean the dot product
is the question just computing the scalar product of those two vector or is it more than that? maybe you messed up a previous step
I need to find the Volum of point A(1,0,0) B(4,-3,4) C(4,3,4) and D(0,0,3)
The Crossprodukt of AB and AC is [-28,0,18] and AD is [-1,0,3] and Whenever I dot those I get 78
But when I try to do it without calculator I get 82
you messed up the cross product
I did? I double checked in the CAS calculator and got the same as when I did it on paper.
can you show your steps?
you mean the volume of the parallelipiped formed by AB,AC,AD?
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hello again,,,, I've been staring at this for a few minutes and can't figure it out😔
Unless it's just trial and error again where i need to list out every locker
given a locker number, how can you tell which students will change it?
If it's a multiple of that number?
what number is a multiple of what
call the locker number L and the student number S. which one has to be a multiple of which?
L has to be a multiple of S
right
so a locker L will be toggled by precisely those students whose number is a divisor of L, yes?
yes
i kind of get the basic concept but it gets confusing when the numbers get bigger
if a locker is left open what can we say about the number of times it has been toggled
is that like after the first student opens them all
does that count as one toggle
or is closing the locker the first toggle
both opens and closes are toggles
what i mean is after all the students have gone and done their thing
and we look at one particular locker that got left open
so then its been toggled an odd number of times?
how many times must it have been toggled
yes
so we are looking for numbers with an odd number of divisors
i seee
think about what those look like
think about how the divisors of a number can pair up
?
sorry i don't understand 😔
if they have an odd number of divisors does that include 1?
ofc, because, in the question, "student 1 toggles every locker that is a multiple of 1"
for a positive integer n, there is a natural correspondence between divisors (if "a" is a divisor of n, then naturally, one other number is a divisor of n)
that is one way to think about it, but the correspondence they had in mind is the following: a is a divisor of n if and only if n/a is a divisor of n.
so this is a natural way to pair up the divisors, a with n/a
i seee
think about how this pairing can be used to prove that the number of divisors of cartain numbers is even.
