#help-23
1 messages · Page 80 of 1
writing it on its own is just something you would do for defining notation, it isnt uncommon to define notation by writing for example $$\dv{x}\equiv D(\phantom{x})$$
i see sinx a lot in math
Duh Hello
it is not, but you can consider it to be at your current level
i wonder if ppl do derivative arguments d/dx without brackets too.. seems risky
rolling the dice
are you doing calculus without having done trigonometry?
no?
just gave that example: sinx should be written sin(x) as x is the argument of sin
for derivatives or for trig functions?
for both, sometimes i do sometimes i dont
i don't see how writing derivative without brackets could be safe
how do you know when it ends?
if there are other terms after it
what if you have $\cos(\omega t+\phi)$
Duh Hello
no there i would, like i said it depends
lol
for derivatives
Duh Hello
consider b to be a function of x
oh man, that's playing with fire
what if it was intended to only be d/dx of ax
not b
how would you know?
i wouldnt add it to b 💀
yeah
I think you should always use brackets for derivatives
no i just put it on b aswell
what about if you have a disgustingly long equation?
like 10 terms
are you writing that d/dx 10 times instead of just putting 2 brackets?
d/dx 10x
i might consider it
lol
i mean it doesnt really matter as long as it is intrepretable
yeah, but if you are taking up massive space with unnecessary notation then eventually you wanna start to reconsider the way you are writing things
idk is never happened to me really
where i thought i have to, atleast not from what i remember
for example in later math you get stuff called tensor notation, so what you could write as this, while it doesnt look pretty im not sure you wanna see what that looks like in normal notation
this is roughly 1/3rd of that when expanded
take shortcuts where you can, they will be useful
obviously dont make things confusing by doing that, gotta keep clarity as well
Imagine marking this
yea i havent stumbled upon tensor notation
Boreogadus saida, known as the polar cod[1][2][3] or as the Arctic cod,[1][4][5] is a fish of the cod family Gadidae, related to the true cod (genus Gadus). Another fish species for which both the common names Arctic cod and polar cod are used is Arctogadus glacialis.
exactly what i was thinking umbra
Ong
Nice to see the Wikipedia references included in the homework
I wonder if there is a website to check if ChatGPT wrote something
probably an issue for homework now, Wikipedia is the least of the teacher's concerns
oh that's good to see
by the same makers of ChatGPT
so they would be able to spot it perhaps even with 100% accuracy
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Hello! I need help with a problem. Let 𝑎∈ℤ. Prove if 3|𝑎2, then 3|𝑎.
I was thinking on starting this problem using a contradiction, but I'm just a little unsure
what is a2? is it 2*a?
write out what a|b actually means
there is another way to formulate it that is more helpful
dont use = when u dont mean it, just plain words
Not at all, however.
a|b means 'a divides b'
if a divides b, then b is not congruent to 1 mod a
no
oh so 1/4?
no....
Maybe dont use it until you learn it properly
I see now
its not 36 either
then what it is
forget modular arithmetic.
If a divides b
then that means ka = b for some integer k
agreed?
that is the usual definition
ok, you should use this
for your question
Write out what it means if 3 divides a^2
and also what you want to show, which is 3 divides a
use this directly
that 3 |a
which is
3k = a
ok, but best to pick another letter
l
because its probably not the same k
j
3k = a^2 for some k
Need to show
3j = a for some j
Ok, now remember a j k are all integers
no, nothing like that
oh alright
So what I would think about is prime factorization
this is number theory so probably not root it
3k = a^2
divide by a?
what can u see in terms of prime factorization
what does prime factorization mean
Intro to Math Reasoning
its strange they havent covered that first
before this
or is this another language
so maybe u dont know the word?
like 12 = 2^2 . 3
not an insult to your intelligence at all
im questioning whats been taught on your course
because there are certain things that should be covered before u talk about other things
and its a pain if it hasnt
this is the prime factorization of 12
2 squared times 3
its splitting it up into a product of primes
no, i dont mean in terms of variables
so just talking about squares
when u prime factorize squares
each prime factor must have an even power
oh I see
u knew this?
So for example 36
6^2?
,,2^2\cdot3^2
thats the prime fac
each prime has an even power
yes
thats the prime fac of 3
Back to the original question
the point is the left and right are equal
so they must have the same prime factorization
yes?
3k = a^2 for some k
So taking this
and taking what i said about squares
you can deduce something about the prime factorization of k
k has to have some integer ^2 power?
Each prime factor in a^2 must have an even power
im not gonna hold you bro we have not covered anything even close to this in class lol
very strange to me
maybe theres an even simpler proof im missing
or they want something simpler
but like i dont see it
Maybe theres some given facts in class u can use
to do this that avoids all of this work
yeah hold on I'll type something up real quick and run it by you
But regardless, this all should really have been covered before
Would this work?
Proof:
Let a=3. We can then say that a^2=9. In this case 3|3, and 3| 9.
Is there a way to disproof the statement?
Let 𝑎∈ℤ. Prove if 3|𝑎2, then 3|𝑎.
You start with any integer a
and so u need to prove this works for any a
right so consider what the power of 3 is like
on the right
it must be 3^(2x)
for some integer x
So now what about the power of 3 in the prime factorization of k
mmm
could we break this proof down into 2 cases
in which one is even
and the other is odd
What is even and what is odd
a = 2n
no, it has nothing to do with a being even or odd
I see
do u get whats going on here
ive written 3k as a product of primes
a product of primes which all have even power
k itself can also be prime factorised
im saying we are interested only in the power of 3
on both sides of the equation
3^1
its 3^1 times k
right
So on the right u have 3^2x
on the left u have 3^1 times 3^y
where 3^y is the power of 3 in k
does that make sense?
yeah it does
,,3^1\times3^y = 3^{2x}
,,3^{1+y} = 3^{2x}
ok?
yeah
🤯
ngl, idk either
lmao
u have to explain these ideas
more important is to understand them first
before attempting to write it
,,3k = a^2
You had this. k is divisible by 3
yeah
and u end up with this which is what you wanted to show
ngl, I have little idea what they expect from you in the class
So it is hard for me to judge what is or isnt good
In the end, its best to hear the feedback from them directly Id say
It doesnt matter if you score highly or lowly - the feedback given is what matters. I have no clue what they're after.
why isn't it 3m = a
,,9m = a^2
here I can get u something real quick
square root both sides
,,3\sqrt m = a
no its this
ohhhhh
I see now
and then the square root of m is r^2
or sorry
m is equal to r^2
m = r^2
yeahg
the reason u can do this is because m is a square
because of the previous way u wrote the product
urgh its hard for me to explain over text
nah I get it
yo I gotta go get some food rq
is it alright if I brb for like 15 mins?
i gtg
oh shit
maybe someone else can look
👌 maybe the feedback can give a better proof than the one i outlined
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hello could i please have some help
Please don't occupy multiple help channels.
okay sorry
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So for this i’m not sure what i’m missing
it’s probably smt very small
F(x) sits description of sinx
so g should be at sinx
arcsinx
integral arcsin^2019x from 0 to 1 but i gs t a huge # that’s probably wrong
well
under the assumption that any function satisfying these conditions gives the same integral (which i don't think is the case) can't we just let f(x) = x?
Wait
that’s true
so integrand is jsut x^2019?
apparently the ans is small between 1-24
there's not enough information
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guys, help
sqrt(15^2 - (3sqrt(2))^2)
$\sqrt{15^2 - (3\sqrt{2})^2}$
Ann
Yeah, sure
I have a exercise from geometrty
please answer the question i ask you.
Wait, wait
I have pyramid base is quadrat, pyramid base square = 72cm^2, pyramid apothem = 15cm, find the height of pyramid
If square = 72, the side of the pyramid base = 6sqrt(2)
then we have right triangle, the hypotenuse = 15, and 1 side = 3sqrt(2)
okay, and what is troubling you?
by that she's asking you what's preventing you from simplifying what you initially gave us
nothing troubles you?
It's sqrt(207), right?
if nothing troubles you, then why are you here?
Because the answer which I got is wrong
Okay, it's troubling
did you copy down the correct values?
are you looking at the answer key for the correct section?
what's the expected answer?
a^2 = c^2 - b^2; a = sqrt(225 - (3sqrt(2))^2)
sqrt(207)
pics of the original problem would help
anyway,
sqrt(207)
can be simplified further
this is going to be a long shot, but are you Russian
Not Russian
and/or do you speak Russian
Yeah, I speak
давайте тогда продолжим по-русски, если не против
ну, я русская.
итак, проблема состоит в том, что у вас есть задача, которую вы решили, но ответ не совпал с ответом в задачнике. так ли это?
Да
скиньте условие и заявленный ответ
Периметр основания правильной четырехугольной пирамиды равняется 72, нужно найти высоту пирамиды, если апофема пирамиды равняется 15
так
Периметр равняется a^2 * 2
что такое a?
Значит а = 6
Сторона основания пирамиды
а с чего бы периметр тогда 2a^2, а не 4a?
Ой, точно, 4а
тогда а = 18
Имеем прямоугольный треугольник, с нижним катетом 9, гипотенуза 15, sqrt(225 - 81) = sqrt(144) = 12
Стоп
Я понял, в чем ошибка была
ну так я вроде бы на нее вам и указала
Спасибо большое )
Можете еще с одним помочь?
ну давайте
Ученик в 1 семетре получил оценки с математики: 8,7,9,8. Какое количество оценок 10 он должен получить, чтобы среднее значение всех оценок было 9.5
Кроме 10 никаких других оценок он не должен получать
так
Я не понимаю, как составить уравнение
чтобы составить уравнение, сформулируйте, что из себя представляет неизвестное
попробуйте сами. если окажетесь неправы, я поправлю
Даже не знаю как
что в задаче требуется найти?
Количество оценок 10
именно так. в нашем случае неизвестное -- количество полученных учеником десяток
прекрасно. так давайте назовем это какой-нибудь буквой, например x
вы знаете, как находить среднее набора чисел?
Нужно все числа суммировать и разделить на количество чисел
Лучше разобрать
хорошо
итак, ученик получил оценки 8, 7, 9 и 8 (всего 4 штуки) и 10-ки в количестве x штук. сколько всего получается оценок?
Это получается (8+8+7+9+x) / 4 + x = 9.5
во-первых, скобки неправильно стоят
а во-вторых, вы заставили ученика получать не десятки, а единицы
еще вокруг знаменателя скобки не забудьте.
А как заставить ученика получать десятки?
тьфу, не туда нажала
а чему равна сумма x слагаемых, каждое из которых 10?
все-таки может быть 10x, а не x?
10x
ага
(32 + 10x) / (4 + x) = 9.5
в чем затык?
Не понимаю как решить
32 + 10x = 9.5(4+x) -> 32 + 10x = 38 + 9.5x
(1/2) * x = 6
x = 12
ну да...
Теперь решилось
как удивительно
пожалуйста
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✅
sqrt^3 -- кубический корень?
Да, именно
Я хотел поднести оба числа к 3 степени, тем самым убрать корень
И получилось бы 64, но правильный ответ: 4
128^(1/3) / 2^(1/3) = (128/2)^(1/3)
А почему так нельзя?
а вы что, просто возвели в куб и числитель, и знаменатель...?
Да
ну так вы всю дробь в куб возвели, конечно же
А
Тогда это действительно правильно, спасибо
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hey guys do u plss give me any resource to learn probability from basics to advance
@blazing kindle Has your question been resolved?
see #books and/or #book-recommendations
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hi, I was wondering how I can solve this without any differentiation:
$\lim\limits_{x\rightarrow1}x^{\tfrac{1}{x-1}}$
CWolf
let f(x) = x^(1/(x-1)), then log(f(x)) = log(x)/(x-1)
I'm not sure I follow
f(x) is what you want to find the limit of
i am suggesting that you find the limit of its logarithm instead
Yes, and you apply L'hopital.
Wish I could, but we can't use any sort of differentiation :/
Just an arbitrary rule or you haven't learned differentiation yet?
We haven't learned it yet, so we're also not allowed to use it
Maybe we're supposed to bring it back to a standard form of e if possible
not even the definition of the derivative...?
Nope...

I'm actually curious about how one would solve this without differentiation. I would assume you have not learned how to use logarithms to simplify problems.
you must know either $\lim_{t \to 0} \frac{\log(1+t)}{t} = 1$ or $\lim_{t \to 0} \frac{e^t-1}{t} = 1$
Ann
I'm gonna assume that's what he's looking for
thanks 😄
That makes my original equation e^1
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Okay I think I get what it is
I think he wants us to let x = (1+1/y)
which turns the whole thing into
$(1+\dfrac{1}{y})^y$
CWolf
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I want to be clear on something here.
I have these two matrix:
What kind og matrix are they? B is not a upper triangular matrix and C is not a lower triangular matrix right? But they are instead anti-diagonal, please correct me if Im wrong.
Also, I had to calculate the determinant. And I know when a matrix is either on upper or lower triangular form you can just multiply all diagonal-elements. Does that also work with "all" anti-diagonal matrix.
Because I can calculate the determinant of C by multiplying all diagonal-elements correctly as: det(C) = -3*(23(-1))9 and -3(23(-1))*9 = 162
If I had to calculate the determinant of B, I would not be able to just multiply all diagonal-elements as it gives a result of -22, but I need 22. Which is why Im calculating like this:
Is there a rule with, if you have an odd number of negative values in the diagonal you need to multiply with -1 also, when multiplying all diagonal-elements?
@desert axle Has your question been resolved?
@desert axle Has your question been resolved?
<@&286206848099549185>
you can just imagine it as switching the columns
each time you swap two columns you change the sign of the determinant
in the case of B you have to swap once, 1<->3, so you get a factor of -1
in the case of C you have to swap twice, 1<->5 and 2<->4, so you get a factor of (-1)(-1)=1
How can you tell which you had to swap?
I mean I could have also swapped others
but this seems like a very obvious choice here
Oh yea sorry, I get it
it turns out that you always have to swap either an even or odd amount of times but that's harder to see
what
Ohh
If had to explain the type of these matrix both B and C, would I describe them as anti-diagonal?
@peak estuary
upper left triangular or something. calling something anti-diagonal if it includes values that arent on the antidiagonal is not a good idea
but why are you encountering a lot of matrices like that
are you sure that you cannot simply reorder the columns?
I can, it's just that I want know what kind of matrices they are - if they had some special name. I'm calculating the determinant, I also have to include text with it - so I was just wondering what I could explain regarding the matrices and with that include some kind of title for the matrix
@peak estuary
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Hey, I’m not too sure where I’ve gone wrong on this
Apparently the answer isn’t correct
Yes
,w int from 1 to 5/2 of 4x^3 - 20x^2 + 29x + 10
mhm, maybe post the original problem
Here
,w roots of 4x3-20x2+29x-10
The intersections are ok
It's asking for the area, so you have to make sure you get positive areas
from 1 to 2, the function is positive
Then from 2 to 2.5 the function is negative
Area must be positive, so you just take the absolute value of that result, and add it to the integral from 1 to 2
It stays above the x axis between 2 and 2.5 no?
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Not saying it's a good idea to do so, certainly not.. but could you use the quotient rule to solve this?
or it needs to be function divided by function to use quotient rule?
Actually let's take it back..
I think I can see these rules
all kind of come from the Product Rule
One Rule to Rule Them All
Fun fact about differentiation rules: it's never wrong to apply them
x/7 could be written as (7^-1)x
More like 1/(7/x))
you could use any of the rules if you can turn it into that form
That's what I meant
This is then subject to the chain rule and the quotient rule for instance
wait, it's not ((7^-1)x)/1 ?
Also
I'm bringing 7 from the denominator up to the numerator
not talking about d/dx here, just how to rewrite this
or 1/7x^-1
but i don't see how it could be this?
Dividing by a fraction is multiplying by the reciprocal
x/1 * 1/7 ?
I will write this out, may be easier for me to see..
$\frac{1}{\frac {7}{x}} = \frac 11 \cdot \frac {x}{7}$
Stephen
Always a good idea with fractions
Interesting...
I need to work on that last one more
but it's true
it's like pulling a 1/1 out of any expression (can always be done)
If you take your fraction
And take it to the -1 power twice
You flip the numerator and denominator
Then put it 1 over
interesting...
I think it's the third example is the hardest one to interpret, but maybe because I'm just not used to it
obv x/7 is gonna be the easiest form
anybody find 1/(7/x) really easy to see what it means? or takes a minute
It's often overlooked in 7th grade yes
I try to keep my fractions only 2 high
But after middle school ? Cmon
Any more gets confusing
if you apply numbers to it , it becomes quite intuitive
1 / (1/2) for example
I think this is fair
,calc 1/(1/2)
Result:
2


Stacking fractions on fractions makes it a bit hard to see things
this is good advice for you avid
For everyone
Sometimes it’s not possible but I will try my best always
well, if I treat division like multiplication (reciprocal of the second term) it makes total sense
But we were talking about uselessly complicating an expression
but I think an extra step is happening here, which is why it can throw ppl off a bit
(a/b)/c is the one I’d struggle the most with
yes, true
I always put that as (a/b) * (1/c)
(a/b)/(c/1) = (a/b) * (1/c) = (a/bc)
we all learn at a different pace. no need to feel bad when comparing to others
Math is THE subject where you can't afford to not know the stuff you've seen before
Bad teachers or not. Can't afford
To be really really proficient at arithmetic and manipulating fractions, indicies and forms of expression can get you a very long way in math
tbf it can somtimes be hard to undo a terrible foundation
Especially all throughout high school
Yes. That's why a lot of people are bad at math. I didn't say it's easy to fix. Only that it's necessary to keep studying math
i you write fractions like this $$\f{a/b}{c}$$then its fine to have fractions within fractions, but $$\f{\f{a}{b}}{c}$$is horrible
Duh Hello
I do that too
a/(b/c) = (a/1) * (c/b)
but if I saw it like this, I don't think I would know.. is fraction in numerator or denominator?
That's when big fraction lines come into play
Extremely cringe and definitely make the main divider bigger
it will change the answer right?
Clearly 1/ by the size of the lines
oh ya it's like 2 pixels bigger, i didn't see that at first
Never done that
Brackets are really helpful, use them
Wdym @obtuse jackal
@sand minnow yeah this is better practice to avoid skyscraper fractions
I just use longer fraction lines
$\frac{\frac{a}{b}}{c}$
brackets are a requirement for latex
mateo713
Latex does it just like me
I dislike using / for divide outside of 1 line text math
Latex formats it okay
can you format like this with latex?
Yes
Use /
oh
@fickle trail look at this message
You can see out people formatted things
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How do you even start with this question?
Thoughts: By Lagrange's theorem, 18 | G and 24 | G => lcm(18,24) | G
so 72 | G?
@thorny dock Has your question been resolved?
@thorny dock Has your question been resolved?
yes
but now thats not the order of H cap K
H cap K is a subgroup of H and of K
@thorny dock
so this should tell you all you need
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Suppose ammunition costs approximately $0.30 a round (the exact cost is not so relevant, but I hope it motivates this question). Suppose I model the trajectory of a bullet after it is fired from a firearm as v'(t) = -g*e_2 - f(v), where e_1 is the basis vector pointing forward, and e_2 is the basis vector pointing upward, and f(v) is some function to be estimated. Note that f(v) = kv is typically used at lowish speeds and f(v) = kv^2 gives drag at higher speeds. It's anticipated that f(v) will be somewhat continuous. We don't have any fancy technology, except a protractor / angle measurement device and a GPS unit. Perhaps in the future, we'll acquire some sort of accurate timing system if we need it, but basically this means that we can only measure two things:
- the angle that the bullet is shot at
- the starting and ending positions of the bullet, but only to a reasonable accuracy (let's say we're only about accurate to 5 cm).
We, however, are allowed to fire perhaps 500 rounds out of the firearm at varying angles, keeping in mind that the firearm also has some intrinsic inaccuracy.
Are these measurement devices enough to estimate:
- the muzzle speed of the bullet
- a curve for f(v)?
My gut says no, but I don't have much more than that. What's a good way to estimate/interpolate f(v) without expending too much ammunition? Something like fitting a spline through whatever points we get?
(this is like part 4 of a really long discussion with country hillbilly friends of mine who own firearms)
@misty bay Has your question been resolved?
given that you basically only know the distance it travels before falling down to the ground
Why do you want to estimate drag
how would you distinguish from the scenario where there's high drag and a high muzzle speed or low drag and a lower muzzle speed?
You know the angle too
You’d have to ignore drag to keep it simple
clearly I can't do that
what would integrating f(v) give
how would it give impulse
Oh sorry I thought f was a force
it's proportional to force, yeah
I think you can do something with it
Find either the change in velocity or the acceleration from drag
Find the surface area of bullet, air density, etc
what would that tell me?
The drag equation
that would only allow me to possibly extrapolate f(v) to other bullets
Based on v
and I probably will do something like that, but for now, I'm concerned with only one bullet
Yeah
or rather I have 1000 bullets that are identical
We’re only talking about one bullwt
what are you talking about
f(v) = kv
this issue here is that the drag coefficient is not a constant coefficient when it comes to bullets
this is why you cannot say that f(v) = kv or f(v) = kv^2
How come
because it just isn't
So then f(v) is like parametric?
in particular, there's a marked difference in drag when the bullet goes from the supersonic to subsonic
f(v) is probably some weird-looking curve
this is a math problem
Sounds like physics to me
the stuff about drag is just for context
but ultimately this is just a differential equation with some undetermined stuff, and you're given points of a very specific form
Can you abstract your question then to a purely mathematical question
I literally did
you were the one who wanted to say that f(v) = kv, and I told you why that doesn't work
I thought you were going to use different ones at difffernet launch speeds
Not midway through
I have identical rounds, and I cannot feasibly control the launch speeds, and measuring them directly is actually pretty painful to do, so I'd prefer not to
yeah I get that now
This is definitely something physicists could also do so I don’t think it would hurt to ask there as well
physics is mostly math
Plus they have experience with your context
That’s all I’ll say
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idk why but when i complete the square, and even try the quadratic formula, i get 0.835 as my positive answer, but its not right and idk what im missing, can someone pls help? ty
What formula are you using?
@covert merlin
!status
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
This seems correct, what did you do next?
i did this but i dont think its rihgt
It isn't
What is the standard form? Can you recollect it?
like this?
This is the formula but what needs to be the original equation to apply this formula?
ax^2 + bx + c
Forgot the equals to zero
Anyway, now tell me what is a, b and c in your original equation?
oh mb
a = pi
b = 5pi
c = -20
oh
OH
wwait imma do it agaiin
and see
👍
wait so
i think i did smth wrong again
i definitely did something wrong
wait im like
BIG dum
omg
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No problem
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@halcyon plover Has your question been resolved?
<@&286206848099549185>
<@&286206848099549185>
Very Sorry
<@&286206848099549185>
hello there, do you still need help with your question ?
( a,b)(e,f)
(c,d)
it says to perform matrix product
does it mean that you'll have to multiply the two matrixes for you to answer the question?
No
oh ... then i don't really understand what it is asking
I think we just have to setup
Yep
do you have any workings to show so that we can check it?
Alr
Alr
that'll give you better chance having ppl to answer.
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@keen peak Has your question been resolved?
<@&286206848099549185>
@keen peak Has your question been resolved?
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What's the probability of winning 1st, 2nd or 3rd place in a contest with 10 players by random chance (all players having the same chances of winning)?
3/10
i think he meant separately, like 1/10 1/10 1/10
yea
i saw
of desired outcomes / # of possible outcomes but im confused
is it
1/4 (given you could not win either of the three)
no, this is the sol
then in percentage it would it be 30% chance of winning and 70% chance of losing, correct?
if winning means standing on the podium somewhere, then yes
so we have 3 winners in your case
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Hi guys i’m stuck here, i need to find BS, AB is parallel to DE, i found that i could use pythogras to find BC, which could help me find CE cuz DEC and ABC are like the same thing, and then i can find DE with pythagoras, but after that i’m stuck
@frail elm Has your question been resolved?
<@&286206848099549185> :(
you can caluclate DE. can you?
you can calculate DB, can you?
DS:SB = DE:AB
wait one second please, i’m going to try
I come out on BS ≈ 9
I took another way than what the answerbook said, but i still got it right, thanks
.close
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How could I prove this identity in the least amount of steps?
(Only using trig.)
I just keep trying to solve it and it expands to ridiculous lengths without ever finding a solution
wait
I think I got it, actually
the identity of tan(a-b) is (tan(a)-tan(b))/(1+tan(a).tan(b))
the formula on the left is that but with a+b instead of a
so I write it as tan(a+b-b)=tan(a)
it was so easy
.close
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How would I start off this problem
do you know what being a member of that vector space entails?
do you know what "(x,y,z) is a member of V" means?


