#help-36
1 messages · Page 27 of 1
♡LexQa♡
who cares if it is a proper subset

Since it is not a proper subset, it is not possible for it to be closed as a subset of $X$
♡LexQa♡
if my knowledge is correct
Surely the whole space is closed, no?
no because the complement of X its the empty set that is open so X is closed
X is both open and closed in X. same for the empty set being both open and closed in X
i see
well back to the original question, can we assume the statement is correct then?
well like u said, there was no provided counterexample
HELLO
just because I can't think of a counterexample atm does not mean there isn't one lol
yeah fair enough
this channel stays open until then ig
I found this on stock exchange
i guess thats it?
wait you're unmuted now 
yep i am back into the world snow 
@tranquil pine Has your question been resolved?
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- How spread are the college students’ weights to the mean?
is this variance or SD?
oh
- How dispersed are the scores of the students from 100 respondents?
i answered SD
is that also variance or only SD?
Both measure that lmao
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$\frac{x^2my^n+1}^3{x^3m+1y^n}$
Zyme><SOL
$\frac{x^2my^n+1}^3{x^3m+1y^n}$
```Compilation error:```! Missing { inserted.
<to be read again>
}
l.57 $\frac{x^2my^n+1}^
3{x^3m+1y^n}$
A left brace was mandatory here, so I've put one in.
You might want to delete and/or insert some corrections
so that I will find a matching right brace soon.
(If you're confused by all this, try typing `I}' now.)```
can you take a pic of the problem
It's (x^2m y^n+1)^3/x^3m+1 y^n
just take a pic pls
i suspect that there are multiple issues with notation
too many to be able to know what's intended
my best guess is
i need to simplify using exponent law, it says answers should be expressed with positive exponents
ℝamonov
what have you tried?
not much honestly, other than cubing what's in the numerator
show me what you've done, whatever little it may be
so the new numerator would now be x^6m y^n+3
that isn't right even assuming you have ()
oh
how are you getting the y^(n+3)
I learned from previous questions that the exponents inside the bracket multiply with whatever exponent is outside the bracket
yeh...
that was my best guess though, I didn't really know what I was doing
you didn't multiply properly
oh
yeah probably, that rule worked when there was only a number as an exponent and not letters too
the rule applies regardless of the number of terms in the power
you just need to multiply properly
so multiplying wouldn't be 3x2 and 1x3?
${(a^{\text{this}})}^{\text{that}} = a^{\text{(this)}\cdot\text{(that)}}$
ℝamonov
you should be multiplying 3 to the entire n+1,
not just whatever part of it you feel like
so 3n+3?
so if that's what you meant it would be (x^6m y^3n+3)/x^3m+1 y^n
I'd assume you'd have to then cancel out the terms
x^3m y^2n + 3 / x^ 1
that isn't the answer though
$\frac{(x^{6m}y^{3n+3})}{x^{3m+1}y^n}$
Zyme><SOL
ok
${(x^{3m-1}y^{2n+3})}$
x^1 = x
so I think we can remove that
or no, that's wrong
we'd have to move the 1 up
Zyme><SOL
this is the answer, last step I really just got the inference by looking at the answer
anyways, thanks
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Please don't occupy multiple help channels.
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hi
could anyone explain why i cant use my integral to calculate the surface area of the area outside the curve r(theta) = sin(theta)cos(theta) and inside r=0.5
my integral:
and the solutions:
this is the graph btw
@pulsar stirrup Has your question been resolved?
$r(\theta) = \sin(\theta) \cos(\theta)$
barometer
yes
1/2 sin (2theta)
<@&286206848099549185> or @midnight ginkgo 🙏
Sorry I'm trying but my internet keeps going down
oh shit okay np!:)
its a formula for surface area for polar coor
So you have the same as the answer key
is it the same case here? cuz ive made another one nd i used another formula again
maybe? i can't really tell what's going on
essentially the formula that you used in the first one is just a partially-worked out double integral
the answer-key writer just converted $\sin{\theta}\cos{\theta}$ to $\frac{1}{2}\sin{2\theta}$
barometer
and also changed the theta bound to pi/4 and multiplied by two bc of symmetry
Ah damn thank u ! so if this would similarly be the same too then?
(sorry for asking sm qs about these )
what are these 
omg im so sorry hahah its 3 sin theta to 1+ sin theta
okay lol
i'm not sure since you're changing the bounds here
yeah no
the bounds on the second integral would be pi/2 to pi/6, not 0 to pi/2
oh okay.. would you possibly know why i cant use these bounds in my integral? bcs i chose r going frm the circle to the cardioid , nd for theta i chose the bounds -pi/2 to pi/6 bcs thats where they intersect
oh i misread that
should be -pi/2 to pi/6 for the bounds in that case i believe
oh i see why you're doing 0
so then itll probably be my r bounds that r wrong for it to result in a diff answer?
do you have the answer key?
yeah
oh fuck😭ithink i found where i messed up
where
oh word
tysm for checking the first integral tho !
yeah
honestly i can't remember on the second one 😭 been a minute since i did that
no wait
huh
yea no i just double checked too
it should be right… right?
cuz were jus substracting
the green
mmm
i think that should be covered when you do the radial bounds
do you know what the answer is supposed to be?
nono i put it in red there cuz i thoight mine wasnt equal to that😭
oh it's not
they literally just did the area of the cardioid minus the area of the circle for that intersection
i think you can't do it with double integration because the angles aren't the same at the intersection points
huh why not
lemme make a little diagram
so at A, the 1 + sin(theta) is at the angle -pi/2, but the circle is at the angle 0. so even though they intersect, it's not at the same angle
oooooooooooooooohhhhhhhhhhhh
thanku sm that was confusing me way too much than it should
me too
i think once you learn double integrals it's hard not to want to just use them all the time lol
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What number should come after 1, -3, 5, -7, 9, -11, 13?
-15?
stay on your own channel only
@golden sundial Has your question been resolved?
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just a quick notation question, but is there any major difference between those two signs?
the first is what i use usually for approximations, but the second i also see from time to time and i vaguely remember some sort of difference 
i dont know their particular names to look them up haha
I’ve seen the second one used for isomorphism
yeah same
okay ty
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me back
hey so in here wont there be infinite solutions?
i hav made this desmos graph, wait lemme share
what they've asked for is when they dont meet right?
Maybe it was a typo
oh no
yea maybe
there are lots of them

wait but then too answers dont match

in the key answer is given 4
@sleek edge Has your question been resolved?
yea and another at 2-3i with 1/n radius
vs a circle centered around 2-3i with radius 1/n

so it seems like they'd intersect when n/4 + 1/n < sqrt(2), right

or no greater than
yea
but the set should be naturals n such that n/4 + 1/n < sqrt(2)
which should be finite

n=1,2,3,4 checks out
Their radii are 1/n and n/4
problem makers made the same mistakr I did then ig
Assuming sum of radii ≥ distance guarantees intersection

what's also needed, and probably forgotten: difference of radii ≤ distance
hm i dont get it
oh
ohh
ohhhh
icici
ahh
so its wrong q?
i mean
infinite sol
ye
right?
should be
i mean even otherwise we still do get infinite solutions no?
nah then you'd get only solutions to n/4+1/n < sqrt(2) as solutions
Those are the cases in which the 2 circles are outside each other
np
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May I have some help getting started on this one?
I cannot figure out where to even begin lol
@wet hornet Has your question been resolved?
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Can someone help me with this one: Let {fn} be the Fibonacci numbers. Prove by induction that every third Fibonacci number is an even number. (Hint: Assume f3k is an even number.)
Where are you stuck? Show work
Im struggelig to formulate a proof for the odd numbers and whole numbers
because the pattern is: odd, odd, whole
But honestly idk what to do next
I think this doesn't need any cases
use the property of fibonacci numbers
$f_{3k+3} = ?$
numbpy
use fibonacci property
.
yes, you assumed it to be true for P(n) for induction hypothesis
Then you want it to be true for P(n+1)
or P(k+1) which means f_{3(k+1)}
yup
yess change it
so it is: f_3k + 3
right?
Im srry but i do not quite understand what you mean with "change it" in this instance
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?
I meant in the picture
Anyway
Use the Fibonacci property on f_(3k+3) twice
Yeah the fact that f_(n+2) = f_(n+1) + f_n
Dudeeeee, nah why did you separate + 3 from the index 😭
No, meant like f_(3k+3) = f_(3k+2) + f_(3k+1)
I think you are confused with the indexing
$f_{3(k+1)} = f_{3k + 3}$
numbpy
This is wrong
You have 3k+3 NOT 3(k+3) = 3k+9
Just work with f_(3k+3) remove the brackets. They are confusing you
Why do you have 3k+9?? Look at what you have written. It's clearly wrong
Like let k=0 then what you have written means
f9 = f6 + f3
because i asumed that f_3k = a whole number
You mean an even number
yup
Just work with that
so should i add that with f_k?
because i need to prove that every third fibo number is even
Yeah, that's why we are using induction
THE INDUCTION IS ON k in 3k
Not on 3k itself
but what can i do with: f_3k+3 + f_3k ?
Why do you have + f_3k?
because that is our asumption
and to find the third number we need to ad the to before that
Huh? Our assumption is that f_3k is even right
yes
Absolutely no need to do that
Just start with f_3k+3
Expand it using Fibonacci property
f(3k+3) = f(3k+2) + f_(3k+1)
Yess, finally
Now, apply the Fibonacci property on the first term again
ie on f(3k+2)
how can i do that? I understand that the fibo property is: f_n-1 +f_n-2 but how can i apply it on the first term
Just remember this, reduce the index by 1
do you mean: f(3k +2) = f_(3k+1) + f_3k
Yep
f(3k+3) = f_(3k+1) + f_3k + f_(3k+1)
Simplify a little
can you simplify it. Everything is written with indexes?
You can add something
or did i mess up again?
Do you realise you have completed the proof almost
to be honest no, but
See the right hand side
yes
Does it look even?
yes because we asumed that f_3k was even. And the first thing is multiplied with 2, which means it must be even
so have i done it now?
Yes cause the sum of two even numbers is also even
correct
nice. Thx for your patience and help
Sure
@dull comet Has your question been resolved?
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hi!
if you didn't know there is a physics discord
oh I tried it there but they said I’m not allowed to post assignment questions
oh
@silver cedar Has your question been resolved?
it should just be the difference of those two lengths no?
actually not quite 
should be these two 
@silver cedar Has your question been resolved?
hi!
yes I did path difference between incident - path difference between reflected
yeah you should be able to get those lengths with trig
Path diff. 1 should be like: dcos(40°) right?
yeah I got dsin(50°) but it’s the same I think
Wait that's not it
d is gonna have to be divided into a big section and a smaller section
So that you can use right-angle trig
Oh you got d already
oh sorry! I forgot to mention I got d as 10000nm
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hey there
so in here what does largest interval mean 
@sleek edge Has your question been resolved?
,w 1 + 1

wait


no but 2 cant be
yeah

bruh

why not give (-∞ ,∞ ) 

\cci -\y,\y 

,tex \def\cci#1,#2 {[#1, #2]} \let\y\infty $\cci -\y,\y $




what if we cheat a bit
lets say
p(x) = x⁵+x⁴+x³

i mean we don’t really know much about f n g


but being a multiple of x^2 + x + 1 necessitates
because f and g are poly
so you only have cubic
and one above cubic
so 3k and 3k+1
so you need 3k+2 to cancel

shopping rn so im doing this in my head 
idk 
$1/3 \le g(1) \le 1$
like
Disorganized

like you can only ever cancel something in the middle
by FTC....
This integral is equal to g(3) - g(0)
oh wait it’s another question
^^
what if we multiply n divide by (x-1) 

.rotate
so its x³-1 in denom
.rotate
,rotate

Oh

and the 3k+2 term looks like a+b+c
the x^2 term is gonna be a+b+c coeff
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how do i do this
which part?
i cant even do the first
okay well let's go through this step by step
ok
first off
i think it will be good to write down the coordinates of all named points
A, B, C, D, P, Q
ok
this will help us for all parts
so let's just get this done so we can refer to it later
would you like to try doing this on your own or should i give you pointers?
don't omit the parentheses
okay, let's see
okay, yeah, all your coordinates are correct
now for part a
you are asked to find the equation of line AB
you know the coordinates of A and B
find gradient
do you know how to write the equation of a line through two points with known coordinates?
finding the gradient is one step along the way
what do you mean by "a random y value"...?
,calc -60 - 20*21 + 480
Result:
0
ok yeah that checks out
it will be more convenient for us to have it in slope-intercept form. can you convert it to that?
ok, good.
that does it for part a.
are you able to continue for parts b, c and d?
how would i find the depth of r?
is its jsut 40
?
wait no
i need to find or
isee
would or just be x=0
so you sub it into ab
and find the depth like thaat?
wording...
i've highlighted in red the depth they ask you to find.
yes
i don't like the way you worded this but your calculations and answer are correct.
you are told to assume that your curve has equation y = ax^n with a and n yet unknown.
you know that the curve passes through A and B and you know the coordinates of both
so what would i do with that info?
what are the coordinates of A?
oh
wait hold on
my bad
the curve passes through C and D, not A and B
yes
-60,18
(-60, 18) yes
ok, can you write down as an equation the statement "The curve y = ax^n passes through the point (-60, 18)"?
yes that is exactly what you would do.
o
a * (-60)^n = 18 and a * 40^n = 8
ok
do you see how to proceed from here
simultaneous equation?
... sure
typo and missed pair of parentheses, also inefficient approach
better to go (-60)^n/40^n = 18/8
from which you will get n = 2
how do i get it into that form?
divide one of these by the other
gtg
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for 1(a), to find the turning point whats the method to use?
is it completing the square?
yeah
,w vertex of y=(x-1)(x-4)
no unfortunately, you have the y coordinate incorrect
why?
What did you get when you completed the square?
oh i get it

ok thanks
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,w turning point of (x+3)(x-1)
in future you can go to wolframalpha.com and ask him directly
but yes that is correct
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hello can someone help me to do that ? I didn’t understand anything
^rotate
,rotate ccw

partial sum formula for a geometric series?
@distant quest Has your question been resolved?
okay
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Do I really need to make a 4 atom truth table or is there another way to do this
you could use a truth table, or logical equivalence laws
@toxic tree Has your question been resolved?
Yup logical equivalence lass would be the way to go or you'll be writing a truth table of size 2⁴
Distributive law should get you a long way
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$\lim_{x \to 0} \frac{x}{ \frac{-x}{1+x}}$
Mehdi_Moulati
like this ?
just use division sign and brackets
@upbeat jacinth what are your pronouns?
Mehdi_Moulati
@upbeat jacinth Has your question been resolved?
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i need a hint with this example. i need to simplify this:
@dark loom Has your question been resolved?
what does : represent in this context?
it's division
never seen it like that interesting…
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<@&286206848099549185>
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Please help me with geometry homework so I can get an A
I wasn’t here the days we went over this and the second one is a quiz correction
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huh
@inner charm what's with opening and closing channels?
im dont open this!
its about 30 minutes



im in lofi girl channel dont disturb
(;´д`)ゞ
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Can you show your work
Like take a picture
Look at this step
ohh hwhoops
Your right
You missed the parenthese though
ok give me a moment I'm looking through the rest
Did you solve sin(x) = -1/9?
But I'm a little confused too because that's more than pi/2
yup
lemme pull up desmos
The answer of pi/2 was marked wrong
okay
it wants the decimal i think
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it says R is an equivalence relation
and x is a non empty set
show that for elements out of X either this option or that option is true
Show that equivalence classes are either identical or disjoint
Well, assume they have a common element and use properties of equivalence relations
Yea $[x] := { y \in X : y R x }$ usually for $R$ being the equivalence relation
chartbit
As per here, assume $z$ is such that $z\in [x]$ and $z\in [y]$
chartbit
ok in my book it is only covered by 2 sentences
wait what is this example about?
@tulip coyote
is it to teach me how equivalnce classes work?
i am confused af
it says to either show they are the same or that they are disjunct
Yep basically, they're telling you to show here that two equivalence classes are either identical or different
oh
To do that, if we have this, we have that $zRx$ and $zRy$
chartbit
Can you say something about x and y now?
Let them have a common element
but ok for R it means it's reflexive, symmetrical and transitive
What we aim to show is that if they do, then we're forced to have the equivalency classes being the same
hmm ok i tried to watch videos on those classes can't find anything useful
you took a z out of the class [x] and [y]?
Basically equivalency classes are the set of all elements that are equivalent to each other
and then compared the z R x and z R y?
So if an equivalence relation is a way of saying things are the "same", an equivalency class is the set of each things that are the "same"
does this mean everything in that set is the same? like {1,1,1,1,1,1}?
Not quite, e.g. let's take the relation $R$ on $\bZ$ to be $xRy$ if $(x-y)$ is divisible by 2
chartbit
Then the equivalence classes basically turn into $[0] = {\ldots, -2, 0, 2, \ldots}$ (the even integers) and $[1] = {\ldots, -3, -1, 1, 3, \ldots }$ (the odd integers)
chartbit
You can choose any other odd or even integer to represent each equivalence class as appropriate
ok wow this makes things even more complicated now -_-
e.g. You could choose $[69]$ to represent the odd integers or $[420]$ to represent the even integers
chartbit
cuz in that example [0]and [1] would be disjunc
Yep that's kinda the point of this exercise 😉
but in my exercise we don't know what R is
Take any equivalence relation, and then you want to show that it'll hold
we have no info about R
You don't need to know what the relation R is, only that it is an equivalence relation
What properties of an equivalence relation can you use here?
ok i get that is the answer but why
See these ones you said
Why do the classes have to be disjoint or identical, or?
i mean i can't know
because you can enter different numbers or x or y
Equivalence relations $\sim$ are such that:
$a\sim a$,
$a\sim b$ if and only if $b\sim a$, and
if $a\sim b$ and $b\sim c$, then $a\sim c$
yeah i get all of those
chartbit
but what changes if i show that for z R x or z R y
You have that this is already true. Hint: use the second one on the first relation, then you can use the third one
What happens then?
z R x, x R z
and then...?
(swap them around and you'll see something!)
Actually wait hang on no
x R z, z R y, x R y?
Yes this!
hmmm
You have that x is related to y, which is what we want
Do you see why that will force the equivalence classes to be identical?
but in this case it would be wrong right?
hmm
Hmmm, not really, they're disjoint, which is what we said, they're either identical or disjoint
but in our case how do we know we can get that z ?
what guarantees that we get that z out of x and out of y
What we said is that if two equivalency classes have a common element, then they must be the same
We don't know that one exists, but as above, if it does, then they're the same
ah ok so it means we are not done?
we only say if that's the case then they are identical otherwise they are disjoint
We pretty much are, provided you explain this here!
Just one element in common is enough to force them to be the same
E.g. consider the classes $[420]$ and $[0]$ from what I said before
chartbit
ah ok this was still just theoretical though right? we can't say anything further than that because we have limited info
Pretty much, we've just shown what they said to, that two equivalency classes must either be the same or disjoint
ahh ok
These two equivalence classes have elements in common
you are right
But e.g. $[69]$ and $[420]$ don't under my relation beforehand
chartbit
Nice nice, does that all make sense now? 
yeah it does
but still i am not sure if i would have found that way to proof it myself
but i guess i should always check those definitions first
Yea a good place to start would be to work with what you know, like the definitions of equivalency classes and equivalence relations here
Then see if you can use those to get anywhere, a lot of proofs are like that
There are some which are more complicated but something like this is just definition finessing (there is a subtle point I guess about why "one element in common is enough to force them to be the same" is enough, but meh
)
yeah i think spamming examples will make me better in this
i noticed i understand things better by doing examples rather than just rewatching the lecture
thx dude 👍
No worries, my pleasure 
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hi, for integrations with improper fractions, is it possible to use only partial fractions instead of long division method for all functions?
@weary mist Has your question been resolved?
hello @weary mist
i am assuming you are talking about functions in the form of
P(x)/Q(x) where deg(P)>=deg(Q)
am i correct?
yes
well, i do always use partial fractions fashioned method to tackle such problems
but I'm not sure the name for it
e.g.
(x²+1)/(x+1)²
i would simply do
(x²+2x+1-2x)/(x+1)²
in stead of doing
(x²+1)/(x+1)==A+B/(x+1)+C/(x+1)²
what about these type of function
(2x^3 + 4x^2 + 5) / (2x^2 + 1)
oh, i will push them one by one , well, actually it's more like long division
for your example
this
I'll show both methods for your example
(2x³+x-x+4x²+2+3)/(2x²+1)
= ((2x³+x)-x+(4x²+2)+3) )/(2x²+1)
= x + 2 + (-x+3)/(2x²+1)
and
(2x³+4x²+5)/(2x²+1) == Ax + B + (Cx + D)/(2x^2+1)
ah
and solve for A,B,C and D
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Try drawing a diagram.
Things will become much clearer.
What is a major segment of a circle
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