#help-39
1 messages · Page 232 of 1
Length of train is just length contraction (or dilation here)
How has distance been obtained, cant tell you where i dont understand because I cant start it
@fringe robin Has your question been resolved?
since the plane and the front of the train are approaching each other in the frame
(w+u)t represents how much the distance between them has decreased at time t [ or should i say it represents how far they have collectively travelled]
taking T to the time when the plane reaches the front
so (w+u)T represents the total length of the train (in the frame)
then the distance between them is the difference between the two
so (w+u)(T-t)
in short:
(w+u)t, distance travelled towards eachother at t
(w+u)T, total distance they will travel towards eachother before they meet
(w+u)(T-t), distance left between them at t
oh so for this bit i don't even need any relativity, just say what you see
yeah
and it looks like the next bit is just equating but my ipad ran out
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why do we have to add the value of the initial position? aren't you already technicially getting that by integrating from 0 to 3?
the integraiton means the distrance travelled from 0 to 3
but we need the strating value to "anchor" it
u need to find da constant for x(t)
yep
wdym by "anchor" it?
Imagine I told you I traveled 100 feet, and asked you "where did I end up?"
that makes no sense unless I also tell you where I started
OHH rightt so you would need to add the position you're already at in order to answer that
perfecttysm
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i found the line of y2 but then
i forgot what to do after that
<@&286206848099549185>
I would approach this with vectors
they're both tangeant lines, so you could express them in terms of r
huh
whats tangeant
someone come back its due in 30 minutes 😭
They meant tangent i believe
A line which touches a circle at exactly one point is a tangent to the circle
i see
how
does that elp tho
uh i cut the thing in half to make 2 right trianges is this helpful or useless
tbh idk, is that the full qs, are you given anything else as well?
wait is OA on the y axis and OC on the x axis
Your circle is centered at (r, r) with radius r which can be defined by:
$(x - r)^2 + (y - r)^2 = r^2$
You can take one of your tangents $y = mx + c$ and substitute into that equation to eliminate either y or x.
Since it's a tangent, the resulting quadratic should only have one solution (indicating only one point of contact). For such a quadratic, the discriminant is 0
StrangeQuarkAL
I think that's sufficient to find r
I personally wouldn't do it that way cuz it's kinda tedious tbh
yeah
whats the EASIEST way so solve this
in the next 26 minutes
Are you familiar with vectors?
uh not rlly
this is a similair problem that i had to do
and my math guy wants me to do it ina similair way as to this
probably
huh
i thought it does
i was thinking like
"how does math guy want me to do this"
and last time there was pythagorean theorem and alla that stuff
im not sure, maybe it could let me try some stuff
like do you know the property of tangent makes right angle with radius
not the entire Quad
did not know that
ok nvm, if you did you could use it here and then distance bw centre and point would be sqrt(2)r by pythagorean theorem
oh kay
hmmm, this seems tough without the property
aw shucks
Fairly easy way:
You know both y1 and y2 and therefore you can find point A and C (they are y and x intercepts respectively). If you show that AC passes through the circle's origin (r, r), simply finding the intersection of y = x and AC would be sufficient to get a value for r.
wha
which part is confusing
finding the intersection of y=x and ac
Oh yeah, (r, r) lies on y = x and AC right?
for y = x: sub in the point (r, r) -> r = r which is true so it does lie on y = x
AC is the one that needs some work
The two kites in the diagram are similar
yeah I do
2??
neat
wait
i get the concept
but
i still dont get how to find it.. 😭
im a tad slow at these things
You can find them in terms of r by finding the intercepts
For example, the left side of the top kite - its length is (y-coordinate of A) - r
a= (0, 8sqrt3 -6)?
seems so
c= (0, 2sqrt3)?
yeah
Nope
i meant 2sqrt3, 0
then what
yeah that my bad I'm sleepy
find the equation of line AC
okay
y=4-root3x + 8root3-6?
@fickle schooner sorry for ping but im runnning outta time 😭
what do i do witht the equatoin of the line..
I said it earlier
The intersection with y = x OR sub y = r, x = r
since (r, r) lies on AC
uhh..
How do you find the intersection of two lines?
set equations to eachoter?
Yeah, you have AC and y = x
y = 4 root 3x + ... equals to x
We established that the solution should be r
okay
thanks
HE SAYS I NEED PROOF
that ac goes thru the middle
of hte circle
thisp pmo
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need help
I completed this chart and I wanted to double check to make sure everything is correct
is this right?
Can you not ghost ping me
I’m not helping you even if I could
Don’t ghost ping people
why are you in such a hurry anyway
so i assumed u are active
because this homework is due soon
and i need to hand it in
but i want it to be correct
If its not contributing to something i dont see why you would be bothered, its a learning process. And if it does contribute to something, then we cant help anyway
did you just ghost ping again?
?
i saw it
no i deleted because I mistyped
I meant to ping my friend
to help
but hes offline
right
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not sure how to solve the following linear system:
$$xcos(t) + ysin(t) = 0$$
$$-xsin(t) + ycos(t) = tan(t)$$
diego
diego
but i'm having a real hard time figuring out how to get to that point
alrightt i'll see where that gets me
thank u
okay i'm still not getting very far at all with this
i'm not very good with trig so this is really tough haha
what did you try with it?
i tried multiplying both sides of the second equation by -x/y to see if that got me anywhere (it didn't) and tried setting the right hand side of the 2nd equation to -x/y to see if that helped (also didn't)
alright ill give another push
use x=-ytan(t) in the second equation
i've tried that it gave me something like this $y(\frac{sin^2(t)}{cos(t)} + cos(t)) = tan(t)$
diego
what happens if you multiply by cos?
ohhhhhhhhhhhhhhhhhhhhhhhhhhhh
ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
i see now
i don't know how i didn't spot that 😵💫
thank you for the help
no worries
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I don't understand quadratic equations (Sorry if the questions are in Spanish, I'm Mexican and I'd like some help)
Help? Please
Pi=3.1416 💀
3.14159.. so its correct enough
Yeah but who tf rounds pi to 4 decimals???
welll the area has 4 decimals so
it kinda makes sense
@slate kite u here?
R = 49 cm
Thats also insane, but w/e

yes, sorry
okay, i don´t understand how can i solve it, i´m new in this
@slate kite Has your question been resolved?
Let me translate, i need to rectificate
16- Calculate the time it takes for a body to fall from a height of 90 meters (take into account that gravity is equal to 9.8)
You know the formula of area of circle?
Oh
A= πr² (r=radius)
Well you know the kinematics equations?
You got the
initial velocity , u = 0 m/s
height , h = 90 m
acceleration due to gravity , a = 9.8 m/s²
@slate kite stellar after which you can put it all in [2] formula to get time
@slate kite r u available?
I'm solving it, I'm trying to see what mistakes I make when doing the quadratic equation
It wouldn't need much but your answer must be 18.36 s
I'm not very good at algebra, but I'm trying to get better every day, my goal is to become as great as you
That's the spirit !!!
@slate kite Well did you got the answer by yourself?
I managed to understand the subject, I have not mastered it yet; But I know that with time and dedication I will be able to be better
Yes , I mean that did you understood the question? And having any problem somewhere else?
Not yet, I have no doubts or problems with this, thanks for the explanation
So should I explain it to you?
No thanks, I understand everything, thanks for the help
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Is this right
the calculations seem right but for d it should be let x be +-2π, not let f(x)
fixed ty
do i have to prove the unit circle thing
very high effort 😭 but it appears everything is alright
haha ty
what do you mean by this though 🤔
where i wrote prove
i doubt it
like you’re asking if you have to prove the value of sine 11pi/6 ?
yea like do i have to show something
ah no, don't worry 😔
ah okay
it's like more personal preference from me but i firmly believe that it's not necessary to show it
I mean I’ve never heard of having to probe something like that, but has the teacher indicated that you should there?
it’s just something that’s easily plugged into the calculator
(if you have to prove it’d just be that sin 11pi/6 = sin (11pi/6 - 2pi) = sin(-pi/6) = 0.5 and a similar method for the other one
ah okay yea i cant use the calculator for this haha
that makes sense
also what about the marks on the graph
handicapped i guess 
i messed up the signs here but yeah
sin (-11pi/6) = sin(-11pi/6 + 2pi) = sin(pi/6) = 0.5 **
perfect ty
I’ve been confused whether I got these in the right spots tho
they are
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oh it wasnt easily visible but below the minimum on the left it should be -2pi/3 not -pi/3
good eye! i fixed it thank u
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Assume x is 1 million (1,000,000)
and I only want 6 digits precision
that mean
p = 1
is enough?
my question is with
x = 1 million
are
p = 1
correct?
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How to know if a non-factorisable quadratic equation (D<0) is always positive or negative for any value of x? I want to know this for an inequality question I sent. I want to cross multiply the quadratic but not sure if the sign will change
When D<0, check the coefficient of x^2 (let a) to check. If a>0 it's always positive and if a<0 it's always negative
(if D<0, the quadratic does not touch the x-axis, so there cannot be a sign change)
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I got an answer but its completely different
First the location of C we set g(x) = 0
Which gives us x = +-2, so C is located at (2, 0)
Then we integrate g(x) with limits 2 and 0
G(x) = 2x - (x^3)/6
2[2] - ([2]^3)/6 - (2[0] - ([0]^3)/6)
4 - 8/6 = 8/3
Then to get V we take 4 - 8/3 = 4/3
Now for W we integrate f(x) between p and 2 and set it equal to 2(4/3)
F(x) = -8/x
-8/[p] - (-8/[2]) = 8/3
-8/p = -4/3
8 = 4p/3
p = 24/4
p = 6
Which is not what they got...
Which step did I do wrong?
what is f(x)
8/x^2
you differentiated instead of integrating
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can someone check my working for this
,rccw
chartbit!!!! ❤️
Hiiii 
what is T5 and T6
i thought it was the term number
In order of ascending or descending powers of c?
On another note, how did that 21 turn into a 12? 
💀
omg
i didnt even notice
It happens sometimes 
It does give you a “nicer” number, at least, which seems what the question writer might have intended 
yeah!! it does
i think its descending
That’s fairs, there doesn’t seem to be a “universal” way to order these (the questions I’ve seen always tell you which way they do it!)
ah!! okay, thank you so much for your help!!
also really nice seeing you again!!
Always lovely to see you 
different notation
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are the lengths of the tetrahedron equal to half of the circumference of the cylinder?
yes
@molten ridge Has your question been resolved?
i got the height as (sqrt(3)*pi)/2. is that correct?
does not seem so...
what did u get?
after unfolding the cylinder, this is what it should look like
cant i use pythag to find the length of the height?
if I am not mistaken a tetrahedron have equal side lengths right?
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can someone show me how to do this one?
i know x^3e^x = x^3*sum{0}{infinity} x^k/k!
but im not sure how to get teh terms for the power series
yeah
is there a faster method than just to find all t he derivatievs of f and find a pattern
for the coeffecient
i mean this has e^x so it couldnt be that bad
not really, that's how you do it
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Can someone tell me where I went wrong? I first found the derivative. From the third line, I used a trig identity for what’s inside the bracket
This question is on finding trig derivatives
how did you get from line 3 (the one with parens) to line 4
2cos^2x-sin^2x is not cos2x
2cos^2(x) - sin^2(x) is not equal to 2(cos^2(x)-sin^2(x))
Oh
ohh i see
Should have just expanded honestly
So I shouldn’t have used an identity..
There isn't one
So is the correct answer just the expanded form of line 3?
Well till line 3
It's correct
And thats the answer
If you want all of them in jus sin
Like Ann said, I accidentally thought I could separate the 2 and just use the trig identity for cos^2x - sin^2x
Just write cos^2x as 1- sin^2x
Ok thank you
mhm
Hello again
I don’t get how to do B
are you given any equations for position of a pendulum
Yes
It’s defined as h(t) = Acos(2(pi)(t)/T)
So I worked around with it
I found T to be 1.42 s
I said the amplitude is 8, but I’m not sure about that
Because it’s the maximum horizontal displacement
And I imagined that’s how high or low the sine graph would get
Is that correct?
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Question:
find all points where f(x, y) is continuous.
Hello !
i have no clue how to calculate the limit.
!occupied
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Lelel it’s fine
relax we posted at the same time
sorry bro 😦
Which one? The one as x->y?
yes
but is it even x -> y ?
like isnt it supposed to be (x, y) -> (a, a) ?
oh
Sorry, I don’t really write too formally mathematical wise.
because this is the solution but it doesnt make any sense to me
its all right man thanks 🙂
Recall the limit definition of the derivative.
true but arent limits in 2D world supposed to reach a certain point from all curves possible ?
What do you mean?
That’s for 3D.
Hmm.
it seems correct but its also glitching my brain because x is a parameter itself.
idk maybe i need to change my prespective
good intuition, but the function $\frac{sin(x)-sin(y)}{x-y}$ is continuous so this isn’t an issue
Yusername
Eh.
Maybe treat one of them like a constant.
but its not when x = y
y is the only variable in the limit. x is a constant.
lim (x,y) -> (0,0)
Is like the "path limit"
Which I would tex if I knew how
but isnt it supposed to approach the same number if the limit does exist ?
when you consider y = constant and x = variable you are only tracing one possible curve out of inifinite more
y is the only variable in the limit. x is a constant
At least judging by the notation used above
in solution that i provided yes i agree
but im saying that its not correct
because you are saying x = a and you change the variable y
you cant deduce that the limit exists because you got to an answer from one possible path
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Hello i need help with this math problemMake a calculation based on the data obtained:
You own a restaurant and regularly procure the resources necessary to keep the restaurant running.
Specifically, you procured 200 eggs at 2000 dinars, 60 litres of oil at 9000 dinars and 10 kilos of salt at 1200 dinars. The dependent cost of these goods is 100 dinars, the gross salary 300 dinars, the margin is 2% (16 dinars) and the VAT is 24,48 dinars.
Calculate the price you'll be selling an omelet at your restaurant.
😔
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
VAT is value-added tax, which is sort of the sales tax of the US
We go to online classes and teach sent it in google classroom and idk how to solve it
I feel like some information needed is missing
Like for example, what are the ingredients needed to make an omelette
Egg oil salt
Also what do “gross salary” and “margin” mean in this context
Yeah, but what are the quantities.
the total pay an employee receives before any deductions are made
Thats gross salary
And margin?
1 sec
Also, this is information is essential
What is it in this specific context
I’ll assume it’s saying profit margin, and each omelet must make 2% profit
Which is 16 dinar
Yes
We still need these quantities
Oh wait nvm
Someone set me the answer
Sent me*
One of my friends did it
Sorry for maybe wasting time
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About the implicit function theorem. If the theorem applies, then the equation F(x)=0 has a solution set of (g(y),y) where g(y) expresses the basic variables (lets call them x) in terms of the free variables (lets call them y), but only in a neighborhood of a point c st F(c)=0. It's this last part that I don't get, why would the implicit function exist only for a neighborhood of such a point? What does this mean in practice? Mind you, I've gone over the proof of the theorem so I'm aware of the logical argument, I'm just unable to visualize what this means in application.
My book provides the following example with the unit circumference, could you help me understand from it please?
@fallen flare Has your question been resolved?
Let's consider the example they gave, x^2 + y^2 - 1 = 0. Then, expanding around the point (0,1), you can write y as a function of x when -1 ≤ x ≤ 1 but it fails for x outside that range. That's why you can only write y as a function in a neighborhood of x=0, not all x.
@fallen flare Has your question been resolved?
Well yes but any x belonging to the circle will fall in that range right?
oh well, I see that any x is valid for F(x,y)= x^2+y^2-1, but only in the domain where x is in the aforementioned range can we describe y in terms of it
thanks
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Interesting that those who want everyone always forget the <@&268886789983436800> 
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Vibrations & Control Systems (yeah ik its physics but I have enough helping equity to ask this lmao)
Consider the first image (two blocks, two viscous dampers, two springs)
An impulse I is applied downwards on m2. The goal of my project (partially) is to minimize the maximum displacement of the lower mass, m1 by setting the values of the two viscous (linear) dampers, c1, c2. I'm also trying to perform modal analysis (ie. what damping coefficients make it over, underdamped, etc- but that's secondary)
My EoMs in matrix form are also attached (2nd image). The coordinate system is + downwards, hence a +ve forcing term. At this point I chucked these EoMs into MATLAB to solve the ODEs numerically and iterated through c1 and c2 values to get an optimal set of values for a defined set of k1,k2 m1,m2, and impulse. Fwiw, my m1 = 3.6, m2 = 8.9, k1 = 51500, k2 = 2150, I = 500. All units SI. The values aren't too important though.
With these parameters, and bounding c1, c2 between [0,200], I get an optimal value (value that minimizes the absolute displacement of x1) of c2 around 60, with no significant dependence on c1. However, if I bump c1 up by an order of magnitude to ~2000, the optimal value of c2 crawls up with it to ~120, and then increases somewhat proportionally to c1. Ie. with c1 at around 8000, c2 is optimized at 300.
For the damping analysis, I got the TF of the lower mass as such (images 3 and 4)
I'm kinda at a block at this point. This is a 4th order system, is there any way for me to determine if the system is underdamped or overdamped (ie. can we- either analytically or approximately get some damping ratio and check if its less than or more than 1)? More broadly, does the concept of underdamped and overdamped even apply to a system of order > 2?
The prof "hinted" at working/trying to get the poles, but I'm a bit lost as to what to do with them. For low values of c1,c2- my poles are all imaginary, for intermediate values, 2 real 2 imaginary.
(1/2)
For high values of c1,c2- all real, but still negative. All I can draw from this is that it appears to be BIBO stable.
The primary problem I want to figure out at this point is how can I determine if the system is over or underdamped?
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I have 0 idea how to do dis
do you know what it means for two angles to be coterminal to each other
Naw
Co means together ik
in numerical terms, we say two angles are coterminal if their difference equals a whole number of full turns.
a full turn, of course, is 2pi radians.
does this ring a bell?
@full cobalt
ok well i explained what it means for two angles to be coterminal.
so what you need now is to start from your angle of 19pi/6 and go down or up in steps of 2pi until you land between 0 and 2pi.
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Where do i do dis
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@toxic lichen
i don't know what you mean by "where"
like, where to do the working for it?
paper.
No i mean
U said start my angle at 19pi
And go down or up
In steps of 2 pi
Until i land beyween 0 and 2pi
How i do that
@toxic lichen
ok
well
let's think about it
right now you're looking at the angle 19pi/6.
are you above the range [0, 2pi], already in it, or below it?
Is this on the unit circle?
well yes but actually no
i would rather you think about the number line
and don't overthink it
@full cobalt you still here?
this question didn't really require more than at best a minute of thought imo
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Im not good at dis
And wym number line
uh ann is saying to reduce 2pi?
19pi/6 - 2pi
since if we increase or decrease by 2pi we will be at the same point
.
subtract 2pi
i was hoping he would come to this conclusion himself or at least tell me that he is stuck without waiting half an hour
lol
The hell is rgrhrgr
angry
💀
Yes
yes
work it out first
i would really appreciate if you tried to put some thinking into it, rather than just blindly following some directions you were given
Adding or subtracting 2pi will give us the same position on the circle
cause if you encounter a different problem with a different number
i would NOT want you back at the "stuck idk what to do HELPPP" position
I put it in my calc
do it in pen and paper or ur mind
You don't need to use calculator
I don know how to do it without calc
Bruh just write it down
do you know how to subtract $\frac{19}{6} - 2$ by hand?
Ann
And subtract
like forget the pi for now
and try to recall if you know how to add/subtract fractions
Do i add a 1 on the bottom?
"add" is not a good word to be using.
but if you want to turn the 2 into 2/1, by all means, go for it.
LCM
So then it 17 over 5
19-2 17
meaning they should have same denominator
Ooo
ok ok ok hold on yes
again
work it out on paper, not in the discord chat box NOR in your head
So convert that 2 so that it has the same denominator
@full cobalt did you try to do it in your head there just now?
So 19 over 6 and 2 over 6
No...
on paper, then?
uh
Yes.
it's 2/1 right
also be mindful of the fact that 2/1 is not the same as 2/6
so how can u write that as 2/6
so you really need to go over adding and subtraction fractions, converting to common denominator, all that stuff again
lemme get you a video...
how can u convert that 1 into a 6 @full cobalt ?
This math video tutorial provides a basic introduction into fractions. It explains how to add, subtract, multiply and divide fractions. It contains plenty of examples and practice problems including examples of adding and subtracting three fractions instead of just adding and subtracting two fractions.
Fractions - Basic Introduction: ...
U said they shoulf havr same denominator
https://www.youtube.com/playlist?list=PL0o_zxa4K1BXacPNb33YSOBXUA_PWZ8bf also more generally
but you also need to multiply the numerator with the same number
I jus changed it
Whatever you multiply to denominator multiply the numerator with same number.
So 2 times 6
yes
So 12 over 6
yes
No
You only subtract numerator
Denominator stays the same
You only perform addition/subtraction on numerator
huh no
Shi mb
yea
How do ik when to do dis
we just add or subtract 2pi until the angle is within the given range
So any question in that format
I jus add or sub 2pi
As a fraction
Finding a common denominator
and repeat until it’s in the range
How do ik when its in range
A fractiln
in cases like this where everything is by pi just divide to make things easier for urself
3.167
Its highet
SO basically
And it happens to be between 0 and 2
No i mean for a diff question
And that is higher than 2pi
THen probably they will ask to find the angle >2pi
To make it within 0 and 2
And how do i do that
Add 2pi??
2pi +2pi?
If they give between 0 and 2pi and ask >2pi just add 2pi
Example they give u pi and ask to find a value >2pi similar to pi
Could you tell me what it is
2pi?
uhn o
Pi +2pi?
yes
Das how to get the angle of pi?
U changed it
To make it better suited
Yes that's it
Just divide fractions if u wanna see where it lies and put a pi
19pi/6
can be 3.167pi
which is >2pi
And if <2pi then sib 2pi from 19pi/6
Alr i got it now
Thx mask
ok
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can someone help ques 84 i feel imposible to integral like normal
do i have to change something
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<@&286206848099549185>
I imagine you will need to split this region represented by the triply iterated integral into 2 regions.
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Trying to parametrize this surface
I was thinking I'd once more start off with a parametrisation of the sphere and move from there
so I have $(3 \cos(\theta)\sin(\phi), 3 \cos(\theta\sin(\phi), 3 \sin(\phi)); 0≤\theta≤\pi ; 0≤ \phi≤ π/6$
What a wonderful world !
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How come this NFA rejects 10? What stops you from going q1->q4?
do you even GET to q1 in the first place
i do not see an arrow leading out of q0 that says 1
q1->q4 is not labelled
Ah sorry there should be a 1 there
epsilon is empty word, so they can reach q1
you can reach q4
you cannot terminate at q4
you still have a 0 edge to take
and no edges in NFA means it goes to a sink
which is not going to be terminal state
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hi can someone rate my proof?
10/10
A
/10
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definition of a lineair function:
f(u+v) = f(u) + f(v)
f(cu) = cf(u)
but dont really know what to do tbh
do you know what the function we call alpha f does
so af(u+v) = a[ f(u) + f(v)] = af(u) + af(v) ?
I wish I knew
ok well you have to
otherwise you have zero hope of proving anything about an object which you don't even know what it is
mmm incredibly vague.
ok right
$\alpha f : V \to W$ is the function which maps each $v\in V$ to $\alpha \cdot f(v)$
Ann
ie $(\alpha f)(v) = \alpha f(v)$
Ann
Hmmm okay
write out, carefully and without trying to overthink it,
what it would mean for alpha f to be a linear map
it is not hard and it does not require any heavy lifting at all
so i start with (af)(u+v) and want to end up with af(u) + af(v)?
so perhaps you do
Hmmm alright
so this?
in the first line i think you have a stray equals sign at the very end
ah ye true that one should not be there
also your opening bracket looks too much like a c. yes, sorry, i am bashing your handwriting again.
other than that you seem good to go
go slower 🙂
no
ill make the brackets bigger
c is an arc of a smaller radius and greater angular measure
yes!
Ill take notes of this too
Thank you guys :) really appreciate it
Wait ill close this in a sec i am trying a question that is almost the same
seems so
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how can i find
$\sqrt{-57 - 16i}$ ?
I would like to know how to calculate the square root of the discriminant
comvert to polar form
alternatively, multiply out (a+bi)^2 and compare coefficients
thx ill try both
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<@&268886789983436800>
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i dont think i understand any of this
@uneven radish Has your question been resolved?
you have to add the torque by gravity and torque by F then express it in the form of
I d^2θ/dt^2 = t_F + T_g
using newton's second law (I being moment of inertia)
then the simplifcation follows by subbing in values given
for second part, let -4.9sin(theta) = -4.9theta and 0.03125cos(theta) = 0.03125
you get θ'' + 4.9θ = 0.03125
which you can solve using characteristic equation of the homogeneous equation and finding the particular solution
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I get how to do this question, but im confused about how come we can start it at the origin and everything still works out?
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Doing homework probability questions
Not sure how to show that the recursion goes to what i have for part d
How do i get from part c to d
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@clear orchid Has your question been resolved?
i just need direction for a show that question going from my final answer in part c to part d
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hi
so yesterday i came here asking everybodys help to find a fallacy in the following argument:
Say you threw a body up (no air resistence). At the maximum height it can achieve, we know for a fact that its instantaneous velocity $v$ will be 0, and acceleration will be $a= -g$.
But we know of a formula, $a = v \frac{dv}{ds}$ where putting $v=0$ would imply that $a=0$
rak³en
I still dont get the problem, so I am taking someones advice and will work through an example
lets say we threw it up with an initial veloctiy $u$, then $v(t) = u-gt$.
rak³en
We can solve for $t$ from the second equation $s=ut - 5t^2$ (assume $g$ is $10$)
why multiply by v?
rak³en
that way u get dv/dt
anyhow since we're going up we want to minimise $t$ so we choose $t=\frac{u - \sqrt{u^2 - 20s}}{10}$. Putting this in $v(t)$ we find $v(s)$ to be $$v(s) = u - g\frac{u - \sqrt{u^2 - 20s}}{10} = u - (u - \sqrt{u^2 - 20s}) = \sqrt{u^2 -20s}$$
funny you think dv/ds is defined
hm
im not sure either
ill try too
0 is differentiable.
is this all correct?
anyhow differentiating the below once
rak³en
so we find $a(s) = - \frac{10}{\sqrt{u^2 - 20s}}$
rak³en
o
I see now
$v(s) = 0 \implies s = \frac{u^2}{20}$ but $a(s)$ is undefined for this
rak³en
hmm
this basically
well then how do I know for sure that the equation is defined?
I can say 'dv/ds' must exist
but in the scenario v=0 but I cannot solve for v or s then I cant really know whether dv/ds exists, does it?
<@&286206848099549185> 👆 is the final question
what are you doing
thats why the integral form of this works
huh?
i am asking for help
the third equation of motion
no idea what you're talking about
but
wait
yeah i cant turn the 3rd equation into an integral
are you sure you can evaluate $\frac{dv}{ds}$ at $v=0$?
Percy
thats impossible for all v(s)
?
i dont see whats wrong if we dont know the nature of v(s)
do you have a $v(s)$ to evaluate
Percy
we don't really use the differential form much anyways
well i know that in free fall i do
but what if i dont (or its too complicated)
what is it
i have done it for free fall I am asking more generally
...so you're telling me you're sure dv/ds is defined at v=0 in free fall?
im not
no i know it isnt defined in free fall
I am asking IN SITUATIONS OTHER THAN FREE FALL
where i might not know what v(s) is
then how do i know that equation holds true or not
ofcourse if i know v(s) I can most probably just do what i did for free fall
im not sure if you'll encounter such a situation
if you do you're welcome to discuss it here
do you wish to overgeneralise $v\frac{dv}{ds}$ as being \textbf{definitely} 0 when $v=0$, despite $\frac{dv}{ds}$ not being defined for the \emph{one case} in which you can model it?
...............
a dollar
Percy
nvm
i am troubling myself for no reason
thanks for beating some sense into me
.close
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