#help-33
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Yes, and the loop goes to the right too
cuzi f you draw counterclockwise
reverse
it goes same direction
so its -
wait dis might explain why my sub method didn't work
cuz the signs were off
wait chatgpt did say my signs were off
So what are your final two equations in terms of V1, V2, R1, R2, R3, I1, I2, and I3?
Lol
Yep!
thanks William! i hope you succeed in getting your PhD
I'm in high school 😭
oh damn
Lol
and i didn't even know how to do dis
Now you know
r u going to MIT
or Caltech
MIT campus is rlly nice
its so nice
I'm not American
museum is overrated
Cambridge?
Nope
I'm not lol
😭
Gn
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how do i factor polynomials with multiple variables
so currently my class is learning factoring stuff like
4u^2 + 4u +1
and i understand it (Although im kinda slow at it)
but she said there will be a extra credit problem on the quiz like
w^2 -x^2 -2x -1
and i wanna learn how
I can help
eq?
Like this
i know how to do the problem in the picture
its this thats hard
i learned that little tech heh 🥹
Draw that out then multiply the high pest variables coefficient with the lowest variable coefficient
And put that at top
Then put the number in the middle or b in the bottom
So put another 4 in the bottom
Now you want to find two numbers that multiply to the top which is four and add to the bottom which is also four
Can you give me two numbers?
i know how to do these 😭
Ok then what was the issue?
Ok give me example
So basically solve it like this
At the start don’t worry about the other variable
First factor
so factor one variable first
okie cool
Don’t forget the w squared
ohh okay
You use a squared minus b squared since a squared represents your w squared and b squared represents the x plus one squared
Yes
so
(w-x-1)(w+x+1) is the answer
Correct
gosh thats weird
will it always be like that you think
what if its like
w^2 - 2w +2x +1
is that possible
if possible could you just send a question for me to factor that is similar because i dont know if it will be exactly the same
In that case you would do the same thing
but +2x is in middle
It’s would be a squared minus 2w plus 1
and how do i separate that
could you type/ draw it
Yes when you two different variables, focus on the one that has majority and rearrange the equation if you must towards your favor
why does +2x go after and not before it
this would just factor to (w-1)^2 +2x since were not finding the difference
Correct!!!
okay im getting better at this, ima ask chat gpt to make questions like this so i can practice
do you have any tips for being able to get better at factoring with like mental math?
Asks ChatGPT difference of squares and addition of squares formulas and memorize them. Then you should be good for factoring with those
difference of squares are easy to do tho
So memorize the other one
what about if its like 3p^2 -10p -8
how would you just know how to mental math that
is it just practice?
Multiply a and c which makes negative 24 and put that on the top of an x in your head. Put b or negative 10 on the bottom and find two numbers which multiply to negative 24 and add to negative 10. However, I don’t recommend doing this in your head on an assessment if you’re just learning it as it’s not worth the consequences of missing points on the question.
Did u have any other questions?
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would this be 0/0
and if that is correct is 0/0 nonexistent or 0
0/0 is "indeterminate", which means that it could possibly be any limit and you don't know what it is yet
so you need to do some algebra to make it not 0/0 anymore
this is a disguised derivative
not even that strongly disguised
But you can solve this with addition formula too if you're like that frfr
yeah heh just doesn’t look like d/dx
@high needle
how do i solve it
For the limit
How do we solve the derivative
Cuz i just plug 0 in for h
and i got 0/0
Have you guys learnt the derivatives of trig functions in class
So does this look familiar
BUt idk how this is a limits question can be derivative
To the first principle definition
No
What could you simplify this to
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How do I know (3)^(1/3) is bigger than 1
Anything greater than 1 to any root is greater than 1
$\sqrt[3]{3}>\sqrt[3]{1}$
Alexis_Fx

Any number below 1 couldn't possibly get greater than one no matter how many times you multiply it to itself
You can cube both sides to verify
That’s a better argument than what I had in mind
The cube function is strictly monotonic so it preserves < ordering
Ahhh yeah or that
Also like logically, if the cube root of 3 was lesser than 1, then it would never reach 3 no matter how many times you multiply it to itself, it'd just keep on getting smaller
@compact crescent you still here mate?
There's a very high chance that he's not coming back lol
@compact crescent Has your question been resolved?
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Could someone help me?
please send your question here.
sure, question please.
So, how do we solve this?
do you know exponent laws / index laws
ok can you name the laws that you know
just the laws, we'll come back to the question after this
Yeah,
(a^m)^n = a^mn
a^-n =1/a^n
a^m . a^n = a^m+n
Actually I don't the name of that law
@radiant plaza Has your question been resolved?
ok good. sorry i was away.
you should also know a^0 = 1
simplify the stuff inside the brackets first. then show what you get.
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Given 2 cuboids of equal dimensions (say a <= b <= c), whats the minimal side length x of cube, in which they fit?
I found out that if 2a <= c, x = c
And also that x >= c
And i also know that if 2a > c, then x <= 2a, conjecturing its exactly 2a
Imma return to this later
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Hi, I want to understand how Ray tracing works with math , if anyone knows something about this feel free to tell me!
If you have a light source S, we consider rays coming out of S, they relfect/bounce around and if they hit your camera then you can see them.
The color is of the rays is changed when they bounce of objects.
I don't know if this is 100% correct
But this is the idea
-# I'm also curious, so i'll also wait here
@rugged venture Has your question been resolved?
Usually you start from the camera, since what you are interested in is "what is the distribution of light coming in at this angle"
it's more efficient because it only considers rays that reach the camera
And you only consider rays that hit the light source?
Pretty much. If you have diffuse surfaces, you want to prioritise rays which go to bright things to make your integration go faster.
Surfaces with diffuse scattering
Specular reflections can also be done
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Hello, I have a weird question. Using diophantus' way of finding pythagorean triples, namely (k²+m², k²-m², 2km), is it true that if k and m have 1 as their only common divisor, then the triple created is a primitive pythagorean triple? If so, why? Also, if there is an article written about it, please send me a link or its name
,calc 5^2+3^2
Result:
34
,calc 5^2-3^2
Result:
16
,calc 253
Result:
30
No
huhhhh
our professor told us something like thaf
that*
i understood it wrong then
any idea what he might have meant?
oh lol i thought it was diophantus' formula but its just the kind of equation
ill look it up and come back then
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i keep getting 200/298
But i know its not the asnwer
Show your work, and if possible, explain where you are stuck.
i got the answer now but i got it wrong on the first try because i didn't put parenthesis around 2x+2y dy/dx starting from line 2
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(2x − 3)(x + 5)
_________________ = 0
x − 7
I would expect x to equal -5,7,3/2 however the answer is 5,3/2
My question is: Why isn't the x-7 on bottom when multiplied to the numerator create another solution for x?
Because the original equation still has it in the denominator
meaning setting x=7 gives you division by zero
hence undefined
so when solving a question such as this each group of parentheses gets set on its own as equal to 0?
(2x-3) = 0;
(x+5) = 0;
actually bringing it back for a second, once you find a potential solution you have to plug it into the original question?
In general, $\frac{a}{b}=0 \implies a=0$ and $b \neq 0$. Here, $a$ is a product of factors, so yes, you set each factor equal to zero (zero product property).
Civil Service Pigeon
As long as you don't do steps that could introduce extraneous solutions, you don't have to worry about that.
Ex. If you noticed that $x-7$ being zero is not possible and didn't multiply by $x-7$, then you wouldn't have gotten an extra solution.
Civil Service Pigeon
I see ok so seeing as it was in the denominator I should of ignored it?
In general, $\frac{a}{b}=0 \implies \boxed{a=0 \text{ and } \neq 0}$. Here, $a$ is a product of factors, so yes, you set each factor equal to zero (zero product property).
Civil Service Pigeon
Note that whenever you set the numerator equal to zero, you need to make sure the denominator isn't zero
here, that's a non issue
but if you had something like $\frac{x^2}{x}=0$, then it would be
Civil Service Pigeon
Okay I get it, thanks

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Can someone help me please
@loud temple Has your question been resolved?
i think you can look at 3 cases: cubes in the center (one face showing), cubes on an edge (two faces showing) and cubes in a corner
what is the minimum sum showing for each of these 3 cases?
21?
try one case at a time
The middle is 3, the edges are 7, the corner is 11?
Mk
Ohh
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any restriction as to what a can be ?
does it need to be an integer? Or is it in R or C
probably it's assumed to be positive and real, since they say that e^at is "growing"
if it were negative then it would be decreasing
and if it were complex then "growing" doesn't even make sense
if its complex
is there any app that plots complex functions
like with a vector representation
yea probably but is it integer
because its mentioned as order but how can we say its of the π order idk if it makes sense
i don't see why it should have to be, the definition makes sense if a is any positive real number
same as with like a derivative we cant use non integer
because we call it order
alr
can you tell me any app that shows complex functions ?
i want to see what it would look like
hmm i don't know offhand, can desmos do it?
i dont think it can
i dont see a way to define a as complex
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is it possible ot have a negitive degree polynomial? how would that even look like? Something in the set $\mathcal{P}_{-2}(\mathbb{F})$
BOSS
I mean you can talk about expressions like $1+x^{-2}$ if you want but by definition they're not polynomials
depression
@pine ravine Has your question been resolved?
polynomial cannot have negative degree
That's how they are defined
You know by convention, we say that the polynomial 0 has degree -infinity
It’s the only polynomial I know with negative degree
Huh interesting
I understand not wanting it to be zero cuz euclid division by constants
Yeah well spotted, I forgot about that
It's bc if you multiply two polynomials their degrees get added together
So the degree of 0 has to behave like -infinity
But negative infinity is interesting
Ah that use case makes sense
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LADR puts "of non negitive degree" a lot so i was curious lol
What's LADR?
Linear algebra done right
Also, since lists are ordered pairs does this mean that only elements before v_k apply?
Like technically v_{k+1} is not on here but i imagine it sould sitll apply to that vector?
Firstly lists aren't ordered pairs unless you're a set theorist
And not necessarily
It just says there exists a k
The k+1th vector could be independent from everything else
I mean I was going off this definition
Yeah ordered collection, not ordered pair
but ok it does kinda apply, like here i should think of it as a set?
whoops yeah
but for this set, I dont see why elements after v_k within the list cannot be considered for the lemme
Okay let me give you an example
cool
v1 = (1,0)
ok
v2 = (1,0)
ok
v3 = (0,1)
ok
here, if you take k=2, then v2 is in the span of v1
But v3 is not in the span of v1 and v2
So you can't just use k+1
ok but whats stopping me from writing the list as
(0,1), (1,0), (1,0)
and taking the second coordinate as an example
Oh absolutely nothing
But this implicitly comes with an ordering
If you reorder the vectors then you get a different k
yeah so the notation is implying, because lists are ordered, you can only use the span of elements before k
(0,1), (1,0), (1,0) is still a linearly dependent list in V
let k = 2 here
In this different list, you have to take k=3
this is no longer true
no like lets erace everything before
ok
You feed it a list of vectors
And it spits out a k
If you feed it a different list of vectors, then it might spit out a different k
no the lemma provides that
so in this case k=3 makes it true
Yes
yeah i see what ur saying
oh
because if certain elements are in a span there is always a furthest one
damn ok
makes sense
wasnt thinking hard enough there
tyty
np
is this the proper logic
basically all elements of the list creating the span are before k
i guess ill do the proof to find out
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Something like that yeah
The proof is pretty easy once you properly understand the lemma
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Can the 5 one be solved without substitution
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I need help
!da2a
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question! See https://dontasktoask.com/
I need help with physics
Hi, just post
Just post the problem. Don't say "I need help"
Well are you familiar with impulse
Yes grade 12 physics should have impulse
Well I’m not familiar with it, could you explain it
Impulse is the change in momentum
Essentially
It's also force integrated over time
Okay
What’s next?
Do I have to draw free body diagram for this?
Hello?
I think I would have to do kinematics for this
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Am i setting H up correctly 🧍♀️
!original
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.
@keen wyvern Has your question been resolved?
Hello
did you figure it out or do you still need help?
@keen wyvern Has your question been resolved?
i did not figure it out
do you still want help on it
yes
ok! so first find the intercepts of the two functions
if youre allowed it will be easy to do in desmos
probably not a good idea because i wont be able to on the exam lol
y is 1 and -1
x positive 2
(2,1) (2,-1)
idk i was thinking it was from x=0 to x=1
@keen wyvern Has your question been resolved?
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Hey guys can anyone explain me how to find limits
@everyone
Hi, I’m pinged. How can we help you today?
Ah what
Do you have a specific question about finding certain limit since this one is too board
Just how do you find a normal limit of a function
,
send an example problem, it will be easier to help you this way
There are multiple approaches with respect to different circumstances. You’ll have to provide an example for us to evaluate which one is the most suitable.
I don't know you can use any simple one
I just started learning limits and derivatives and i can't understand a word
@calm harbor @vernal forge
or an extract of the book that confuses you
It’ll take hours for us to give a full lecture.
The most effective way is that you provide us an example
Please use any simple one
simple is subjective :^)
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guys how to solve this ODE?
@fair remnant Has your question been resolved?
maybe the sub v=y/x
Yes
Substitute v =y/x and then solve
Alsp dont forget to check the value of dy and substitute that aswell
i did but
the final integral is unsolvable that way
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hello, another question
in the example given, why does (x + 9) need to be rewritten as (x - (-9))?
they're explicitly writing it in the form (x - c)
most likely to match the defn here.
if you can see that -9 is a root seeing the factor of (x+9), there's no real need
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w0 = [1, 0, ..., 0].
So I am confused about this. Because the calculation i did was (1 + cosθ)^2 + (sinθ) ^ 2 + 2 < 3. This ultimately simplifies to cosθ < -1/2.
cosθ is only less than -1/2 for angles 120-240 and (120 degrees). So 120/360 = 1/3. Im not sure how the probability is being calculated in the problem
also it looks like the solid black arc is the only part we can move to to decrease. by doing simple geometry, i have also calculated the angle of the arc is 120, and 120/360 = 1/3
well they're not asking you to show that the probability is exactly sqrt(3)/4
you just need to show that it's less than sqrt(3)/4
you found that it's 1/3, well gg 1/3 < sqrt(3)/4
Im not sure how the probability is being calculated in the problem
but yeah I'm also wondering how they select the vector, what's that equation 2.31 they're talking about ?, is it just about the w0
yes,
do they describe their random search anywhere else ?
yes, the random search algorithm is just picking a random direction and determining if the direction we moved in is less than the previous point
ok but do they define how they select the random direction anywhere
it's not defined explicitly, but the sense i got is that it's truly randomly selected
@quaint arrow Has your question been resolved?
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And check if they're equal
im not sure how?
( if f(-x) = f(x) or if f(-x) = -f(x) )
By plugging -x into the definition of f(x)
Wdym? If you wrote it correctly, surely you know why
i dont understand it
properly
Why -7(-x)^2 = -7x^2 ?
yes
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Hello math fellows, I would like to have some help regarding (yet another) question I have in linear algebra (sorry I ask too many questions).
So let we have a field F, and we define a linear/vector space V on F.
Next we define a norm on V, and finally we can define an inner-product on it.
So first question, the inner product gives us the geometry?
Next, we have the following statement:
<a,b> = |a| |b| cos(t)
The <a,b> is define from the inner-product, but |a|, and |b| is define by the normed space(before inner-product joins the chat), so does it mean that the structure of the inner-product must be somehow compatible(or inherited) from the normed space?
And regarding the ratio cos(t) = <a,b> / |a| |b|. For any inner-product, and normed(metric) space (F,d), how is this proved that this ratio returns a value in [-1,1]?
Thank you in advance.
It need not be compatible
But it doesn’t make much sense to prescribe conflicting information about the geometry of a space
sorry I ask too many questions
No such thing
(generally, if you have an inner product space and a norm, it's taken that the norm you're talking about is that induced by the inner product, rather than any general norm
)
If $\langle\cdot,\cdot\rangle$ is an inner product then $f(x) \coloneq \sqrt{\langle x, x\rangle}$ is a norm
frosst
Yes, like defining the linear space, then defining an inner product on it which will define the norm as well. Pretty awesome.
So if you prescribe an inner product on a vector space then it immediately also induces a norm
The next question is, why specifically |a|=sqrt(<a,a>)? and not something else maybe?
I mean you can pick something else but then it may have nothing to do with the inner product
Like the statement cos(t)=<a,b>/(|a| |b|) may not essentially return [-1,1]? is it considered broken? or?
Sorry, am a little confused. I'm wondered if this is possible that an inner-product satisfies all of required properties/axioms, but the statement/ratio <a,b>/(|a| |b|) does not essentially return [-1,1], then what? we have a new cosine?
I’m not sure if this works in general
Otherwise, if <a,b>/(|a| |b|) essentially returns [-1,1], then has it been proved already? or how to prove it?
How can you define what cos(t) is if there’s no t on the right side of the equal signs
Good question! now this is even more confusing now... wow! 
I’m pretty sure this only works in ℝⁿ if you take the dot product
There are some nice identities like Cauchy Schwartz
They won’t hold if the inner product has nothing to do with the norm
Another question, so if we have a normed space (X,d), then defined inner-product must satisfies <a,a> = |a|^2 ? or this is a special case in R^n? since I havan't seen such conditions in lienar algebra books.
Once again you can define the norm and the inner product separately
But then they will have nothing to do with each other
A lot of theorems rely on the fact that the inner product and norm and linked
Yes, but we will have a geometry?
Depends what you mean by geometry
Inner products give you an idea of what orthogonal means
To find an angle between two vectors, and orthogonality for instance. The problem is that the distance is found by the norm space, but the angles are found by the inner-product, and they are not linked. that's my problem. what happens? is it actually possible? like we are going to have a chaotic geometry?
What does an angle really mean
That's another question.
There are vector spaces where you can’t just take a protractor and measure the angle between vectors
So they are not inner-product spaces?
For example, consider the vector spaces of constant, linear and quadratic polynomials
(also, as per the previous point, talking about a norm inside an inner product space almost certainly means you're referring to the norm that the inner product induces
)
Verify that this is indeed a vector space
And I can prescribe that $\langle f, g\rangle \coloneq \int_0^1 fg,dx$
frosst
Then this is an inner product on the degree 2 and lower polynomials
Now I ask what does it mean if you ask me the angle between x² and 3x + 1
Maybe finding the ratio cos(t) = <a,b>/(|a| |b|), and t=arccos(<a,b>/(|a| |b|)). Here comes my next question as, the cosine/arccos function must be defined already maybe? or we are defining it here? so if we assume cos() is already defined, then the ratio must return a value between [-1,1], and this means if the ratio returns something out this bound, then the geometry is broken, hence the inner-product still satisfies the axioms. So does it mean we have an inner-product, but we cannot have a proper geometry on it?
You should notice as well that whenever we add structure to our sets we always require it be compatible with the existing structure, for example, a vector space is an abelian group under +, and then you add the scalar multiplication, and the distributivity axioms are the compatibility conditions
It is not guaranteed that your right hand side is between -1 and 1
You can guarantee it if you use the induced norm, then Cauchy Schwartz can be shown to hold, then you can prove the right side is between -1 and 1
Exactly, that's my question as well. We are working with standard inner-product and R^n, and everything is pretty cool and working. I'm thinking more abstarct(at-least trying)
I mean as soon as you get a complex vector space as well, your inner product can return complex numbers
Now you’re trying to arccos a complex number let alone something not in -1 to 1
And this is even when you are using the induced norm
Yes, then we will have another norm from complex to real! The next question is the norm to calculate the abs value of a complex must be induced from the norm we are using in inner product? or could be different then?
Yes, R^n is pretty nice, very nice. That's the problem.
You can certainly prescribe norms and inner products independently, but is it useful to do so? That’s really the question we ask
if you pick the induced norm then yeah on a real vector space you would get angles between vectors
I tried to read many linear algebra books to find my answer, but they didn't go deep that way. For instance, Axle's stated that since norm in the R^n is not linear, so we needed inner-product to inject linearity. pretty cool pov.
Or Friedberg stated that to have a richer structure in order to have a geometry, we need that inner-product.
What does he mean to inject linearity
Well, that's the main question... what happends, and what if we go this way? IDK yet
I’m not sure about that
It turns out to not be very useful
Maybe it is, maybe not. IDK yet. I can't sleep, I need answers.
You can’t do very much when Cauchy Schwartz doesn’t hold
When you introduce norms and inner products it’s because you want to talk about them and how they interact
But if you prescribed them separately and independently then the core theorems that relates them no longer hold
Then there isn’t much you can say because they haven’t got much to do with each other
You have no idea how they might interact because you’ve prescribed them independently from each other
Yes, exactly. But it sounds very interesting.
It is not..
Imagine a vector space defined where you didn’t need distributivity
Can you even prove that -1*v = -v?
Can you even prove that 0v = 0
Great question actually, thanks for sharing your questions and thoughts.
It’s good to give this a think no one really realises that our nice results happen because we forced them to appear
Maybe I need keep studying more. Yes, it's never enough. Sorry for many questions.
Don’t be sorry for questions!
studying doesnt help for math if you dont understand it
Just too curious, and not that smart enough to find the answers easily from resources. But I love math, I have to success.
if you dont understand it continously then might give it up
you dont need to study math in uni
Well, I'm a math student too.
not like im saying anything just im saying im in 10th grade and i dont study/learn anything i get A all the time
and i know uni year 2 things
WHAT
studied everything until uni year 1
you are in 10th?
wow
you didnt know?
grade 11?
no
I cannot get A, have level of infinity during exams. That's bad. But try my bst to understand stuff by studying and studying and asking and asking.
write the topics you have learnt till date by that extra study
lemme see if it matches with me
asking is a very good habit
hmm lemme think i think it was integration by parts
you will learn more by asking thats a good think dont be ashamed of it
ok now
!done
If you are done with this channel, please mark your problem as solved by typing .close
you come dm
Am not ashamed at all, I ask my questions anyway. Thanks.
np im always here to help and im sure anyone that has the helper tag thinks the same!
Thank you @leaden monolith , @glass silo , @proud ice , and @noble geyser . Really really appreciate your time and helps, awesome.
Math bless us all 🤘🤓🍻
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Is this right?
,rccw
y = log(cos(x^2))
y' = 1/(cos(x^2) * ln(10))
is that what it says?
not sure what the 90_ before it is meant to be
He gave y=log(cos(x^2)) and wants dy/dx the second step is from me idk if it’s right
That’s 20 question number my handwriting isn’t the best sorry
long-winded way to say "yes that's what it says"
anyway, no, your derivative is incorrect.
alr
yeah how did you make 2 look like 9 
xDDDD
yeah thanks for the help guys really appreciated
you need double chain rule here
Yeah I don’t think so
is this sarcastic or genuine
@pliant whale Has your question been resolved?
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I am trying to solve this problem on a math/programming challenge website. There were many problems of this nature, but this one was the simplest. I know there is some kind of shortcut to finding the solution, since a brute-force approach would take billions of years to complete. I am looking for some information that would point me in the right direction. I looked at this wikipedia article about prime counting functions. Am I on the right track? https://en.wikipedia.org/wiki/Prime-counting_function
In mathematics, the prime-counting function is the function counting the number of prime numbers less than or equal to some real number x. It is denoted by π(x) (unrelated to the number π).
A symmetric variant seen sometimes is π0(x), which is equal to π(x) − 1⁄2 if x is exactly a prime number, and equal to π(x) otherwise. That is, the...
you don't have to hide its Project Euler xD
lol
anyway, there is no good algorithm to find pi(x) (I don't know any) but there are very good estimates
but they are only estimates
The shortcut is to count all the multiples of 2, then count all the multiples of 3 that aren't multiples of 2 * 3.
up until 10 to the 12?
Yes, it will require some thought to take that and work it into a correct algorithm.
Wouldnt all the multiples of 2 basically be 10 to the 12 divided by 2?
So the answer is approximately 10^12 / 2 + 10^12 / 3 - (10^12 / 6) ?
Well, that's only for the first two primes.
For example, 25 won't be handled there.
For the prime factor 5, you need multiples of 5 that aren't multiples of 2 or 3.
Oh, and it's more like 2 * (10^12 / 2) + 3 * (10^12 / 3 - (10^12 / 6)).
to start off 2 * (10^12 / 2) + 3*(10^12 / 3) ... LPF * ( (10^12) / (Largest prime factor of 10^12) ) then that whole thing subtracted by all the shared factors?
No, you need to handle the shared factors inside each set of parentheses if you do it that way.
Think through the first few primes.
With 2, it's easy since it's the smallest prime.
You do 2 + 2 + 2 + ... + 2, one 2 for each even number.
With 3, it's still pretty easy.
Largest prime factor of 10 to the 12 is 5 correct?
You do 3 + 3 + 3 + ... + 3, one 3 for each odd multiple of 3.
Yes, but why are you looking at the largest prime factor of 10^12?
To give an example of why we can't stop at 5 (if that's why you mentioned it), take 49, for example.
49 is within 2 through 10^12.
right yeah
I know the mod 10 to the 9 means theres some sort of shortcut approximation I can take, because with modulo you lose information after the operation
No, that still requires an exact answer.
The last 9 digits have to be correct, but the only way you'll get them is to do the calculation correctly.
is there some formula i should derive similar to how the sum from 1 to n is the same as n(n+1) / 2?
It also can introduce some complexity, like you might need to reduce mod 10^9 after each operation that can overflow your numeric type.
Well, the best way I can see to do it will have a short algorithm, but it won't quite be a closed form like that.
This is my current code
void main()
{
writeln(S(100)); // This is 1257
}
// Θ(n * sqrt(n)) = Θ(n^(3/2))
public ulong S(int n) {
ulong sum = 0;
for (ulong i = 2; i <= n; i++) {
sum += smallestPrimeFactor(i);
}
return sum;
}
// Θ(sqrt(n))
public ulong smallestPrimeFactor(ulong n) {
if (n <= 1) {
return 1;
}
if (n % 2 == 0) {
return 2;
}
for (ulong i = 3; i <= sqrt(cast(double)n); i += 2) {
if (n % i == 0) {
return i;
}
}
return n;
}
Which completely slows down after about 100,000 or so
Yes, you want to avoid doing it that way because you have to partially factor each of 10^12 numbers that way.
For primes around 10^11, for example, your algorithm will take a long time just for one number.
This is why I recommend starting with the each smallest prime and getting all the numbers (no factoring required), rather than taking each number and getting the smallest prime.
With the prime counting function?
I'm not sure the prime counting function can be used.
That'll tell you the number of primes below each number.
But they want the smallest prime of each number.
Ohhh nvm
So the answer would be every y value on this graph up until x = 10 to the 12?
Yes.
Is this the right track or am I just rephrasing what I already tried doing with my code
I'm just rephrasing
Well, it applies to both my method and yours.
It's essentially what the problem is asking rather than a method of figuring it out.
I'm assuming that's a graph of the least prime in each x.
I don't know a way to do it with an integral. I doubt it can be, but I'm not that advanced in math.
I mean, you can probably do the integral of smpf(floor(x)).
Thats what I was thinking
Can this be solved on paper by hand or does it involve some kind of repetitive, heavy computing?
Well, it can be done on paper, but it'll take a while.
Is it required to calculate fully S(10 to the 12) or is no number that big ever reached?
Well, that's what the problem wants you to find, but there are cheaper methods than finding the smallest prime of the numbers from 2 to 10^12.
is this linear line something of use
Not really. The ones that stick up are just prime numbers, and their height is x.
So, the line is y = x.
No.
I think its out of my reach, I will look at it tomorrow a little more but other than that I think i am biting off more than I can chew
I have to go to bed now
Thank you for the help!
You're welcome.
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number 3
!helpers
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<@&286206848099549185>
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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
@loud temple Has your question been resolved?
2
Uh I think I know how to solve it
For the first part tbh u could just brute force it ish
U already know 10, 20, and 30 can’t be it cuz they already in other rows
And then u look for other multiples in row 7, 8, 9 that are also multiples of 10
I’ll just let u do the rest 😭
@loud temple Has your question been resolved?
fr brute force looks like the only option left 
Fr all 3 can be solved using brute force
2nd one is like just prove smth greater than smth
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hello in this ODE solving for y you can find a particular solution which then if you plug in the equation and take t=9 you get on the left side a number μ lets say and then δ(0) so we get δ(0) = μ in R. Is that not a contradiction ?
and another question is if δ(t-9) = .. arethmitics with functions then doesnt that make δ a normal function but its not ?
(δ is the dirac delta "function" btw)
<@&286206848099549185>
@ornate leaf Has your question been resolved?
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Could somebody check these?
On it
All correct, great job @echo scaffold

But be careful on 49. By your writing, it can be pretty difficult to read whether you meant $\sqrt{x^2+2}$ or $\sqrt{x^2}+2$
Xwtek
Ty!
It just looks like $\sqrt{x^2+}2$, which looks weird.
Xwtek
Handwritten matters too
I remember losing couple marks for being misunderstood cuz of my handwriting🤣
My handwriting is terrribllee luckily I have a typing accommodation on my iep.
It’s not because of my handwriting but it still helps that lol
Lol
@echo scaffold Pls close the channel by using .close if you’re satisfied with the answer
bro u can just see this
like
stare it
carefully
if there are even powers only it is even
if there is only cos function it is iven
if it is reducible to cos it is even
just stare it
like see in its soul
dont put
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I'm entering a competition and I think knowing the quadratic formula is needed. I discovered it is used to find roots and I kinda see them in the old papers.
Does anyone have any tips on remembering the quadratic formula, or why it is like that, like the 4ac and 2a as the denominator
if you know how to complete the square from the general quadratic form $ax^2 + bx + c = 0$, that's exactly how you can derive the quadratic formula.
Lute
Let us find out how the famous Quadratic Formula can be created using a bunch of algebra steps. A Quadratic Equation looks like this:
Oh alr thanks
Also thanks
Also what square?
Also what's an !xy
!xy
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.
oh
Ah ic thanks
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Can someone help me with what to do next? I think im stuck on how to get y’ out of this
Wait.
$$y = 2xe^y$$
Xwtek
Xwtek
$$ y' = 2((1)(e^y)+ xe^yy')$$
Xwtek
mhm
$$ y' = 2e^y+ 2xe^yy'$$
Xwtek
Xwtek
oh
uh
i have this but
maybe iii
erm
...
divide by 2xe^y?
I think you should move the $y'$-s to the same side of the equation.
Xwtek
No, not like that
sorry
Like this:
$y'-2xe^yy' = 2e^y$
wait
oh then divide by y-2xe^y
but, how could we know that we can subtract the 2xey^y*y'
Xwtek
Wait a typo
Yes
wow ty
imma leave this open tho in case i have another quesrtion rq
Ok so i tried another one
Does this look good?
Be careful of the bracketing.
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Ok actually another one so im finding the derivative of this one just a regular one
✅
I think you have made some errors
Mr etienne
The last step too, you cant cross out 2x and 2x, thats like saying (5 + 2)/ (1 + 2) = 5 (because you cross out the 2s). This is clearly not the case
The rule you used was good, but the derivative of x^2 + 1 is 2x
also , personally, i don't like the prime notation on parenthetical expressions, i think it's easy to miss
but that's not a mistake
Your derivative rule for qoutients was wrong
time to redo lol
some students prefer never using the quotient rule btw
and writing instead
f/g=f g^-1
product and chain rule
ive seen proofs other ways
Im saying those are not the correct ways
but anyway its one less rule to memorize, if a student is averse to memorization
It should be seen as a corollary
it need not be
I numbered my steps this time
i memorized it as
If everything looks good now ill dp the algebra
D[f/g]=(f'g-fg')/g²
if yhat helps you
thats what my brain does to store the formula
oh i thought thats what i did
it is
just different order of f'g and without (x) everywhere
this is a memorization technique, not a correction
oki
;-;
so, easy to fix
Step 4 is wrong in the upper part too
this gets a lot more routine abd easy with practice
I think you need to take a step back and think about the steps you've made. Doing extra steps isn't a bad thing if it prevents errors
