#help-23
1 messages · Page 464 of 1
There's a nice formula for finding sector area
Radians express angles in terms of pi
But I’m looking for the volume not area
Rather than degrees
Does it still apply?
I was thinking about going down the volumes of revolution route
yes that route
So rotation the circle around the y axis to produce a sphere
So you must have come across radians?
You can't integrate without them
ohh
Its just an arbitrary angle used for the formula to derive
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how to prove if these groups are isomorphic ?
@kind dove Has your question been resolved?
They are not
An isomorphism is a bijection, and there isn’t bijection between them because the former is uncountable while the latter is countable
Yes
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For a function g: A $ \rightarrow $ B where a = {a,b,c} and B = {0,1} which of the possible options for the function g is 1 to 1.
For a function g: A $ \rightarrow $ B where a = {a,b,c} and B = {0,1} which of the possible options for the function g is 1 to 1.
$For$ a function g: A $\rightarrow$ B where a = {a,b,c} and B = {0,1} which of the possible options for the function g is 1 to 1.
Γιάννης
I don’t know how to do this
|A|>|B|
This question is so confusing
I know this
So?
Yeah
You just said it
Yes
So?
But it doesn’t make sense for the codomain to be smaller than the domain
Problem solved
Pls explain how this works
I don’t know where you got the idea that |codomain| can’t <|domain|
Give example please
What?
…
Because |A|>|B|
I underst
Good
I’m now seeing textbook pages in my mind
I’m actually stupid to make this mistake
But then again
This is a very strange question?
Idk
It seems strange
No strange that it’s 3 marks
This makes plenty sense
I was confusing myself
I don’t know what I can say, good for you? Easy to make 3 marks?
Hopefully that is what he wanted
I also feel that it’s strange wording to ask which of the possible options for the function, without listing any options
The main problem here is that I forgot what codomain was
Show that none of them is injective. Just so meaning less to me
Oh wait
I wouldn’t make such list
I know what they are
You can make it if you insist
Np
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if i integrate from A to D what area am i finding
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I honestly do not understand how to go on with this natural deduction
A is deducible from A in the OR ofc
Damn, I suppose there aren't a lot of people working with this ND system
<@&286206848099549185> Don't rly like to ping, but I've tried 3 times before 🙃
@cold quarry Has your question been resolved?
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is independence the same as association
e.g for a chi squared hypothesis test null and alternative hypothesis
instead of no association and some association
can i write independent and dependent?
@elfin willow Has your question been resolved?
@elfin willow Has your question been resolved?
@elfin willow Has your question been resolved?
@elfin willow Has your question been resolved?
that's fine. as long as you elaborate on your results.
@elfin willow Has your question been resolved?
@elfin willow Has your question been resolved?
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How to proof:
$$AP^2+PD^2+BP^2+PC^2=4R^2$$
Tanjiha
you said that you got it
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@thin token im curious how did you prove it?
well i gave her a lead
even i wasn't sure if it will end up being proved
see this is what we discussed
at the end ig she found out with the lead, but now idk
uno reverse, now I'm curious @supple ore
Damn you uno reversed me
So if we think about the circle in the form X^2 + Y^2 = R^2 then we can get the lengths of our parts like so
AP^2 = (Y + Sqrt(R^2 - X^2))^2
PD^2 = (Sqrt(R^2 - X^2) - Y)^2
PC^2 = (X + Sqrt(R^2 - Y^2))^2
BP^2 = (Sqrt(R^2 - Y^2) - X)^2
If you expand these and add them all together you will find it simplifies to 4R^2
Y being the y coordinate of BC and X being the x coordinate of AD
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heya, function question:
f: R->R, f(x) = x-[x]
Gauss floor function
a) show that f is periodic with the function T0=1
i’m not sure if 0 is the correct answer
So [-3.3] = -4
Yeah
Not a fan
it’s periodic and the minimal period I can find is 1
@teal cape Has your question been resolved?
so the answer is [-3,.3] = -4?
oh forgot the other question
b) show all the possible sets
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@fading kayak sorry for ping, can u see what i did wrong for a
You forget to apply f to the first answer
That is, you only wrote p(x) + q(x), not f(p(x) + q(x))
Same goes for second answer with p(x) and f(p(x)); q(x) and f(q(x))
Same in b
Well, you forgot to apply f everywhere 😅
ohh bc of the lin transfo from P2 to P3?
i should only apply f for p(x) because of P2 to P3 right
No, you should apply it because that's what is asked
You're asked to write the result of f(p(x))
e.g. for the first question :
f(p(x) + q(x)) = x(p(x) + q(x)) = (a2+b2)x³ + (a1+b1)x² + (a0+b0)x
i think i did that and then only applied f for p(x) in part 2
- In a. second answer you forgot to update the second part (i.e. f(q(x))).
- In b. first answer you forgot to mutiply a0 by c
And, finally, yes in fact f(cp(x)) = cf(p(x)) and yes f is a linear transformation
applying f works for any function?
What do you mean ?
nvm but i think im getting it, just confusing myself a bit
i think theres a with a that would make it a lin transformation
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hey
The probability of being a vegetarian and a smoker is .24. the probability of being a smoker alone is .4. given that someone is a smoker, what’s the probability that they’re also vegetarian?
not sure how i’d do this
.4 / .24 = .06
draw a venn diagram perhaps
‘let’
“let”
my logic i guess. don’t know if i’m even properly utilizing the vent diagram
*venn
@lean otter Has your question been resolved?
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Hey can someone help me with experimental and theoretical probability, I have a question I’m stuck on where it’s 12 snails racing, two dice are spun and whatever the sum of the dice the corresponding number of the snail will move forward, for example if it rolls a 9, the 9th snail will move forward. However I’m not sure how to find the experimental and theoretical probability for this
whats the actual question
?
“Experimental” prob just count ways each were obtained and divivide by total
For theoretical do a table for example
What do you mean?
I mean what I said
Can you clarify what you said?
Seeing how you aren’t clarifying on what you don’t understand, not really no
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How/why does the x appear/disappear in the numerators of these equations?
? its just partial fractions
so nothing super magical is happening
although partial fractions are kind of magical 
wait what even are partial fractions
jan Niku (Shuri for Honorable)
make this into a single fraction
so its $\frac{(x-4)+2(x+3)}{(x+3)(x-4)} = \frac{3x+2}{x^2-x-12}$
jan Niku (Shuri for Honorable)
so an x "appeared" in the numerator
partial fractions is the reverse process from the right hand side here
we know this can be split into a sum of fractions
each fraction will have a linear factor in the bottom
well

they wont necessarily be linear
but theyll be simpler
usually
I believe I'm just working with linear fractions for now
idk though my professor did not explain this
so yea heres the question
it sounds like magic, its just algebra
start here $\frac{3x+2}{x^2-x-12}$
jan Niku (Shuri for Honorable)
heres how you start the process
ill get u started then u try on your own, if you want
and confirm it equal to what we started with
yeah that sounds good
It will split into linear factors as long as the degree is no greater than 4
you can create uhh
i mean it might not split at all
you can create a fourth degree with a quadratic denominator tho
anyways
thats not important
You can always split it into linear factors
you start here:
As long as its less than 5th degree
$\frac{3x+2}{x^2-x-12} = \frac{A}{x+3} + \frac{B}{x-4}$
jan Niku (Shuri for Honorable)
now solve for A and B
consider re writing it this way
$\frac{3x+2}{(x+3)(x-4)} = \frac{A}{x+3} + \frac{B}{x-4}$
jan Niku (Shuri for Honorable)
and multiplying through the denominator on the left-hand side (you get many may cancellations)

Is it going to need a little guesswork or is there a consistent formula or something?
I think i can do it with guesswork but if there's a consistent way to do it I think i'm a little confused
so id do like
you multiply through by (x+3)(x-4), yea?
so we got to this
$3x+2 = A(x-4) + B(x+3)$
jan Niku (Shuri for Honorable)
@native jay your real tool to utilize here is that you have two functions of X
they are always equal
so for any x, this equality must be true
lets pick convenient values for x, then
since it must always be true
what happens at x=4?

lets see here
so itd be
14=7B
sounds good 😄
whats the other convenient x value?
alright
Ok I think i've got it
so now you go back just a bit
and back to a million years ago when we started

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Hello Basically my teacher taught this math problem step by step with my classmates solution but I don’t really get the problem it’s self and would want help to solve this
@opal mason Has your question been resolved?
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why do you have 2 rooms
Oh so
I made a mistake
And sent the wrong message
And it was pinned
So i tried to close it
But it didnt
So it was bugged or something
@coarse plover Has your question been resolved?
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@coarse plover Has your question been resolved?
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how to solve for x?
logarithms
just as the inverse of addition is subtraction, and the inverse of multiplication is division, the inverse of exponents is a logarithm
I'd recommend you do some reading yourself since they're a complicated topic but generally the way I convert it is that $base^{exponent} = solution <==> log_{base}(solution)=exponent$
FeO
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https://math.stackexchange.com/questions/2826123/odds-of-coming-out-ahead-in-roulette
I understood the problem, but my answer seems to be incorrect for the first part of the problem
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I wanna calculate the distance between a point and a line SEGMENT, i use vector projection for that and it works unless the projected point isnt on the line segment anymore. Since i want the distance between the Segment it should then calculate the distance between the Point and the end of the line segment
here is an example
the white point is the point i want the distance too
and the red point is the projected point
normally i calculate the distance between the white point and the red point
but here the distance would be to the left end to the line Segment
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hi
my qn wasn't answered before can i ask again
dont ask to ask
no one seems to be helping
Well no one can help if there's no question.
the graph between Aul and lambda is a straight line given in my textbook
flu ,gu,gl are constants
how's it possible tho cuz it has a 1/x^2 dependency
yeah it's not a line
textbook says otherwise tho and i asked my professor
he said it's the right graph
Oh yeah, I can totally see your textbook
and asked me to find the answer on my own
If you want to give the entire context of your question, go ahead
as for rn, I can only say it's an inverse square law, not a line
well this is the graph
beats me idk
the constants dont have an effect obviously do they

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I need help with this one
im getting both +∞ and 0
how?
What I'm gonna say is not rigorous but helps
When x gets bigger, the one that has bigger exponent wins, in this case 5x^4+2x is 'dominated' by 5x^4 so when the x gets larger, 5x^4+2x can be approximated as 5x^4
we dont have to think abt the 2x?
No
That's why I'm saying this isn't rigorous
The formal way is to take commo factor x^4 and so 2x is only left with 2/x^2 and it's limit goes to 0
I did something like this. I have no idea of what im doing
what did I do wrong here?
Divide by x^2 above and below
What?
No
Sqrt(5+2x^-3)
x^-2=sqrt(x^-4)
Divide them by x^2 or x^4?
It didn’t exactly what I told you
Can’t you just do this?
Why are you so stubborn
You don’t understand that a=sqrt(a^2) when a is positive?
I understand that
$\sqrt{5x^4+2x}\frac{1}{x^2}=\sqrt{(5x^4+2x)\frac{1}{x^4}}=\sqrt{5+\frac{2}{x^3}}$
Cogwheels of the mind
Jesus
OOOOOOHHHHHH I SEE
Good
is this correct?
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How is riemann sum used in probability theory?
I know that Riemann Sum is used to approximate the area under the curve, I don't understand how it is used in probability theory
@supple nimbus Has your question been resolved?
Okay thanks! I get it now
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what are the steps of solving this derivative?
Differentiate ln(x^4 +1) and multiply with differentiation of x^4 +1
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There already has been some discussion regarding this previously, but no conclusion came, we basically had a false start.
What the hell am I doing here?
What the hell am I doing here?
No
What?
What isn't?
n=4,this 4 numbers:5,6,7,8
There is some possible value.
10 doesn’t divide 26
I never told it did?
You are saying I am blind?
Ah
Look at what you said bro
Light mode.
Remove.
Right should is not something I should have said.
Relax, I agree on that.
I never said 10 26 thingy.
Just pointed out a mistake
Also, 100% bruh wtf?
I never said you shouldn’t say anything
Just found a mistake and I pointed it out, that’s all
I said, I should not have said should. I should have tried the problem though, lol.
Exactly, that's completely alright.
What we have to prove is
There are
$m \in Z and n \in N$ so that it is divisible, now better?
What the hell am I doing here?
No
m and n are given
We prove the existence of a subset whose sum is divisible by that number
For all m?
I believe m should >=1
Well in any case the first sum is

Because it’s false when m=0, a little error in the problem, we can fix that, just by assuming m>=1
Like I said, it isn’t always that subset
I told you a counterexample already
Forget the should be divisible thingy now.
@potent geyser Has your question been resolved?
I think I’ve got the answer
I’ve tried it through induction
Here’s the pattern
Can you do a proof by induction based on this pattern?
lemme see
bro you should read the chats above by the way, we had a light mode user and a guy that for a moment said that 10|26 argue with each other. They are very smart and kind individuals tho, which makes this funnier.
Tried, didn’t work. those n numbers , there exists one divisible by n, say kn, if I use induction I can find a subset of the remaining n-1 numbers whose sum is divisible by 1+2+…+n-1, but sadly that sum divided by 1+2+…+n-1 isn’t necessarily k. Like {5,6,7,8,9} you have a subset of {6,7,8,9} whose sum is divisible by 10, which is {6,7,8,9}. Sum is 30, 30/10=3 doesn’t equal 5/5=1
you just rewrote the question tho
Induction failed
This problem is very difficult.
after all
Yep
The competitors had 1 week to solve these questions tho
there were 8 of them
Wait what really?
Yeah
Woah.
I have already solved 6 of them
One is above my grade to attempt
This is the last one
This is a previous year prob
Not ongoing
Maybe just send it too. one question we can’t solve or two questions we can’t solve. That makes no difference😂
Yeah, but this is not ongoing, so I have infinite time(theoretically) to solve it
But practically, I have a test in a few days
What’s the another question you didn’t solve I mean
The circle one
You regarding two points and a 90 degree angle
Yes, and thank you again for that
But I was not supposed to, it was for the grade above
I see
I am in 10th, it was for 11th grade students
Didn’t realize competitions are classified by grades, I thought all high school students attend together
I'll try and elaborate on what I wrote
I am part of an 'elite' society of math enthusiast students in India, it is exclusive because they make us take an IQ test and only 145+ scorers can enter. It is shitty and discriminatory this practice. But they give us really cool problems and resources though. Part of this society is solving these questions on a weekly basis. So these are grade based
I see
It is still a shitty society though
thnx a lot
poverty is a prevalent issue in mathematicians after all
¯_(ツ)_/¯
Yeah, I think I'll be giving up on this problem permanently for a while, good luck though
bro, pls dont
Try doing some data crunching and try and find patterns though
not tea
@potent geyser Has your question been resolved?
I am forming an idea, first we can assume that 1<=m<=(n-2)(n-1)/2+n-1 right? Because WLOG We let that sequence be contained in [1,n(n+1)/2-1]. It derives the general result.
Then we actually have the range of those sums, union of [(2m+k-1)k/2,(2m+2n-1-k)k/2]. Where k from 1 to n.So we want to find integers k and s such that (2m+k-1)k/2<=sn(n+1)/2<=(2m+2n-1-k)k/2. So we want to find an integer between ((2m+k-1)k)/n(n+1) and ((2m+2n-1-k)k)/(n(n+1)). Notice that the whole thing is contained in [(2m)/(n(n+1)),(2m+n-1)/(n+1)] except some gaps: [(2m+2n-1-k)k)/(n(n+1),((2m+k)(k+1))/(n(n+1))] , where k from 1 to n-1. So I need to show that number of integers [(2m)/(n(n+1)),(2m+n-1)/(n+1)] contains is greater than sum of numbers of integers [2m+2n-1-k)k)/(n(n+1),((2m+k)(k+1))/(n(n+1))] contain, where k from 1 to n-1. So I need to prove an inequality:gauss floor function [(n^2+(2m-1)n-2m)/(n(n+1)] is greater than Σgauss floor function [(2k^2+(2-2n)k+2m))/(n(n+1)]. Since the right hand side, those n-1 terms , the greatest terms appear when k=1 or n-1, so I am thinking proving
[(n^2+(2m-1)n-2m))/(n(n+1)]>(n-1)max{[(2m-2n+4)/(n(n+1)],[(2n+2m)/(n(n+1)]}
this is trivial
the sum you want it to be divisible by is n(n+1)/2
so it's just gonna be a pigeonhole thing
How?
it's like
if you can't find one that's divisible by n(n+1)/2
then all the possible subsets of that set will sum to something that isn't n(n+1)/2 divisble
and that's gonna be a contradiction somehow bc of pigeonhole
like, there's gonna be 'too many' possible subsets somehow
Why?
if there exist no subsets such that the sum of the subset is divisible
then all the possible sums of the subsets are not divisible
3 and 17 aren’t divisible by 10, but their sum 20 is.
no
say you have subsets A, B, C, etc.
and say the sum of the elements in A is a
and the sum of the elements in B is b
etc.
then, if none of a, b, c are divisible by n(n+1)/2
then all of a, b, c are not divisible by n(n+1)/2
right
it's just logic
Yeah
i gtg, i'll take a shot at writing something up when i get back in a bit
But you said sum to
What does it mean , sum to, like a+b+c?
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@potent geyser Has your question been resolved?
Need help
@potent geyser Has your question been resolved?
so considering modulo n(n+1)/2
suppose m is a modulo n(n+1)/2
then let us consider the possible sums of the subsets
the 1 element sums can be from a to a + n - 1, and all the intermediate values are possible
the 2 element sums can be from 2a + 1 to 2a + 2n - 3, and all the intermediate values are possible
the 3 element sums can be from 3a + 3 to 3a + 3n - 6
the 4 element sums can be from 4a + 6 to 4a + 4n - 10
etc.
and the single possible n element sum must be n(2m+n+1)/2
ok
Yeah
so assuming maximum overlap
like
merge all the intervals, assuming they all overlap
well hmm they don't have to all overlap but
well for a = 1, let's simplify it, there's probs a WLOG argument somewhere
then we have it's just:
from 1 to n
from 2 to 2n - 1
from 3 to 3n - 3
etc.
so clearly these overlap
so in the end it'll be from 1 to n(n+1)/2
so that covers all n(n+1)/2 possible values
bc it's modulo n(n+1)/2
What do you mean merge?
wait i think i screwed up a little
Why they all overlap? Some cases they don’t intersect at all
No I can’t
bet you can, let's see...
And what is the special case you considered? When a=1?
i wouldn't expect it to be especially trivial
it illustrates the general point
it turns out that indeed the sum of all of them is the one that works
? Find a subset of {1,2,3,…,n} whose sum divides 1+2+…+n
but overall you're covering n(n+1)/2 different values
look
i'm showing the general technique
this is what i mean by pigeonhole
it's gonna be a long finnicky argument
essentially you cover all the n(n+1)/2 'holes' modulo n(n+1)/2
I still don’t know why you said it covers all values
it's clearly going to turn out that it does
this is my intuition, i'll follow it through
gimme a sec
Those closed intervals, they can have empty intersection
??
Oh I see
it'll work out
i haven't worked it all the way through yet but this just smelled like pigeonhole from the start
gimme a sec
You still need to tell me why it covers 0 , they are big, they overlap, but they can still be contained in [1,n(n+1)/2-1]
you want to think in terms of maximum overlap and minimum unique values modulo n(n+1)/2
if there are at least n(n+1)/2 different unique values for the sums modulo n(n+1)/2, then by pigeonhole you're done
so how do we show this
that's the question
😂 n(n+1)/2 values mod n(n+1)/2 are just all of them, 0 included
we need to show that we have all values lol
that's all
so
the 1-element subset sums cover n different unique values
well that has to be the case
How will you rule out the worse case
there's way too many of them for them not to do that
something about the structure
That is they are all contained in the longest one
not sure yet
well yeah ofc the longest one isn't long enough
the longest interval is just n different values right
No
if they're all contained within the first one
no wait i'm a fool
it'll be midpoint
yes
ok but
Yeah k=[n/2]
we can deliberately go from the 1-element sums
and add another element and break out of that interval, more deliberately
then add another one, break out of those
Don’t understand
Gl
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Not rlly sure how to differentiate c
Do you know how the derivative of inverse trig function are found?
It’s done using implicit differention.
So you know the derivative of arccsc(x)? If so then apply chain rule.
No, I derive it for you.
Just realized it would be better to watch this instead. https://youtu.be/WFCWtycjKAk
The video proves the derivative formula for f(x) = arccsc(x).
http://mathispower4u.com
thank you!!!!!
Sorry, the explanation by me would have taken too long and wouldn’t be clear enough.
This video is about finding the derivative of arccsc(x). After knowing that, you can do the above problem.
Using chain rule.
All that is left for you problem is multiply it by the derivative of arccsc(x).
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did you try to evaluate the integral?
yeah
i got it down to
integral from 0 to 2pi of sqrt(t^2 + 4)
using trig identities
@pallid nymph
ok
yea that just looks like itll be hard
square root + ln something
looks good
yea
@lean otter Has your question been resolved?
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How fo i work thid out
5
@woeful vector Has your question been resolved?
is the problem to find the x,y,z angles?
try finding the angles in this order
1 2 3 can be found using a line is 180 degrees, 4 uses some theorem i forgot the name of with the parallel lines, 5 is 180 degrees, 6 is the same idea as 4
@woeful vector Has your question been resolved?
you can start with this
i forgot the theorem name but it makes those two congruent
then with reflexive you get this
and then all angles on a triangle =180 so 180-75-55 gets you 50
all angles on a line = 180 so 180-50-55 = 75 (x answer)
i dont remember this theorem either but you get this
again all angles on a line =180 so 180-30 is 150 (z answer)
then the final answers are x= 75° y= 55° and z= 150°
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bruh
It's by 20%*2/5 = 8%
hello is this room free
what
20% weighted with it being worth 2 of the 5 tests
it was a 20$ increase
As an example, test scores: 9, 10, 11, and on the final test 10*1.2. The average of the test exams is 10, the final test is 20% more. The average of all tests is (9+10+11+2*12)/5 = 10.8, an 8% increase overall compared to the average of 10 from the tests
Yes
I just did 20%*2/5 as I knew that the 20% was to be effectively spread across 5 exams where the 20% came from 2 of them/exam weighted as 2 exams. I knew that it would also be 0%<x<20% so if I tried 20%/(2/5) I'd know I was wrong too
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evaluate 1 * 100 + 2 * 99 + 3 * 98 + ... + 99 * 2 + 100 * 1.
I tried to do something like this: 2( 1^2 + 1 * 99 + 2^2 + 2 * 97 + ... + 50^2 + 50 * 1 ) but how do i continue?
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What is root mean squared value?
RMS whatever.
How is it useful?
What's the major difference between that and the regular avg?
Ping me please.
Average is used to get the central tendency of a given data set while RMS is used when random variables given in the data are negative and positive such as sinusoids
Ah, makes sense.
So, RMS is like a straight line which goes from the middle of a sine wave?
Kinda
Yeah, as expected.
Thank you so much!
you are welcome
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Help #2
Sry it sideway
@vernal lark Has your question been resolved?
@vernal lark Has your question been resolved?
@vernal lark Has your question been resolved?
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what is problem asking for
you can just add all the same term then
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hey
quick question, what's the difference between scientific notation and e notation?
are they exactly the same thing?
@elfin bough Has your question been resolved?
@elfin bough Has your question been resolved?
They are the same but in e notation e is used to condense the equation. E is equal to "x10 (times ten)
E.g: 5.94 e 19 (e notation) = 5.94x1019 (scientific notation)
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anyone help?
you have to post the question
what do you think you have to do
idk
any ideas?
You have to solve it like a was an x
So how you solve this
x + 1 = 2
you subtract both sides by -1
x = 1
now what do we do for a + 5 >= 9?
What confuses you?
How to do it
do you know how to solve x+3 = 2
5+3=2?
1+1=2 quick maths
No it’s not 5 because if you move the 3 to the right side, its sign changes from +3 to -3
x + 3 = 2
x = 2-3
x = -1
—
So how you do you solve x + 5 >= 9?
I understand Now ty
Sorry wheat i meant is The whole wuedtion changed
Like it restarted my Thing
and gave me a new set of question
Can you solve it?
minus 8 from bof sides
u want x on its own
so that u have x >= something
the way to do that is minus 8 from the left side
and if u do that, u have to minus 8 from the right side as well
Thank u
no problem
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How do I do number 8
I get a different answer, and since I can look at the answers in the back what i get is not true but I dont understand why
,rotate
what did you try?
you said you got a different answer, what did you do to get your answer?
Oh
so first i got P=4x+4y
then p is 600
600 = 4x+4y
150 = x + y
y = -x +150
used x=-b/2a
x= 75
but the answer says it shoud be 100
why 4x and 4y?
ok, but that middle fence is shared by both areas, it isn't there twice
draw a rectangle
i made it P=4x+3y
ok
and divide it down the middle
don't split it up, just cut it down the middle. Yeah!
so, ok, the perimeter is 4x+3y. Got it
I get 600 = 4x +3y
3y = -4x+600
y = -3/4x + 200
but when i put that into x= -b/2a
like when i put it into area formula
that's not a quadratic
a = x(-3/4x+200)
x=-b/2a finds the vertex of a quadratic