#help-28
1 messages · Page 143 of 1
huh charbit you really love emotes, don't you?
(also saves having to type out responses sometimes lol
)
I'm not sure how to solve
$\int_0^{\pi/4} \frac{x}{cos^2(x)}dx= [xtan(x)]_0^{\pi/4} - \int(tan(x)dx$
uh, the the second part should simply be $\int(tan(x)dx$
Why am. I here
yeah.. sorry hard to keep track
Merineth
hint: tan(x) = sin(x)/cos(x)

can you do it from here?
Merineth
looks right to me
btw, is this dutch ?
it's @next basalt's, posted from before
It's Swedish
ah, ok
Honestly based on the amount of time i spend on this server recently i'll end up with my own channel lmfao 
Some people have like their own threads, in the topic-specific channels, you never know 
You can create your own in help forum
Help forum is more for specific questions, basically like these channels (and "eventually" the channels here will be phased out)
I usually always get help quickly here so I don't need one 
There's something like this thread https://discord.com/channels/268882317391429632/1195800467880558672 and there are others 
i'm also learning linear algebra..
this is way worse tho
I'm desperate for food now tho... so i'll take a 30 min break :)
I'll be back later

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Wow you started like three hours ago, definitely well deserved break I'd say! Enjoy the food 
Enjoy your break! You deserve it after working so hard!
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anyone know how to do this the answer is 4 congruent triangles but i just dont know the steps to get to that solution
I think there's no solution needed no? Just say 4 congruent triangles and you're set
I see 8 but ok
8 of these
the thing is if i js say that my teacher wont accept it
Just say 8
ok
well make it a sentence
what kinda teacher is that
wait hang on
unique triangles or...?
if unique there's 1
and it says PAIRS of congruent triangles
that's why the answer's 4
i think i figured it out
its mostly just reflexive property then vertical angles then by SAS they're congruent
yep
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$\int_0^{\infty} \frac{cosx}{3+sinx} dx = [ln|3+sinx|]_0^{\infty}$
How do i proceed from here?
$\infty$
Steakanator
Enjoyed your break ?
Merineth
DNE i think
Haha yeah i got foodcoma !
The answer says divergent but i don't know what that means?
the limit DNE
That it is infinit large?
no
not in this case
basically sin (inf) is undefined since it oscillates infinitely
so ln of sin inf is undefined as well
thus this integral should, theoretically, b undefined

,w calculate int from 0 to inf of cos x/(3 + sin x)
see
Weird
this is the graph.
it repeats
so at certain points the int is 0
from 0 as in
at others 1
etc
since it'll cancel out depending on the endpoint
inf... isn't defined so
Do i have to type lim every time ._.

💀
You could do something like omit the limits but then "add them in later"
So like $\int_a^N (\ldots) \dd x = \ldots = \int_a^N (\ldots) \dd x \to \ldots$
@devout valley
$\int_0^{\infty} \frac{x}{1+x^2} dx = \lim_{N\to\infty} \int_0^N \frac{x}{1+x^2}dx$
wait latex doesnt have limits? damn
it does, $\lim_{N\to\infty}$
oh i see
Merineth
:( i haven't solved it yet
click the bin
[whole denom is a tiny bit easier, but just a tiny bit!]
it won't make any difference, will it?
@devout valley (ur bio says to ping when replying)
It doesn't in the end, but it may look nicer to use the integral you get with u = 1 + x^2 as opposed to u = x^2
$[ln|1+x^2|]_0^N$
Merineth
good point
no
close
very close
the derivative of x^2 + 1 is 2x, not x
what does that tell you?
that i factor out 1/2
so $0.5 \cdot \ [ln(1+x^2)]_0^N$
Once again the answer is divergent
i think that's how you do it?
ren
yes it is
no
actually yes
since ln 1 + n^2 as n tends to inf is ln 1 + inf = ln inf
that's just inf
so yea
if it were smth else like x^-2 it'd be 0 instead of infinity
Ah i see, since ln goes to infinity so will the integral
[but at the other endpoint, 0, you may have problems
]
hold up
Merineth
"exponentials beat powers", so -Ne^{-N} goes to zero, and e^{-N} should clearly go to zero as N goes to infinity
where did half that stuff cm from
also you left out dx (irrelevant here ik but my OCD is kicking in even with ur awesome, i might add, handwriting)
By parts and evaluating
id see half the parts
oh they just evaluated
isee
*i see
i thought that was the expansion of parts and was confused as hell
Which part are you comparing the exponentials beat powers? 
,w xe^-x int from 0 to inf
"so $-Ne^{-N}$ goes to zero"
@devout valley
You can see that as $-\frac{N}{e^N}$ and the denominator gets larger much faster than the numerator ever will
@devout valley
yep
$-\frac{1}{e^N}$
Merineth
And same goes for this

done?
Nop
||a lot more||
but this is genuinely good practice for me too
and it's fun
LOL
THAT FEELING AFTER THE SPOILER
i love that sticker
I sit here between 13-21 CET
I tend to attempt them before posting :3
,ti --at CET
The time in CET is 07:30 PM (CET) on Sat, 03/02/2024.
chartbit is 1 hour behind, at 06:30 PM (GMT) on Sat, 03/02/2024.
The time in PST8PDT is 10:30 AM (PST) on Sat, 03/02/2024.
chartbit is 8 hours ahead, at 06:30 PM (GMT) on Sat, 03/02/2024.
i am hammered aren't i
||OKAY NOW I CAN NARROW DOWN WHERE CHARTBIT IS LOCATED BASED ON THE TIMEZONE. I'M COMING IN HOT
||
at is just at
LOL
Merineth lifting off to find chartbit
here we see a wild Merineth in it's natural habitat, stalking a mathematics DC server helper
it is primed to narrow down the exact locations of targets that warrant its interest, often soliciting a nuclear or orbital strike
@next basalt next one??
Solving, one moment
Grab food and then come back and lurk 
no im hungry for maths
nom nom nom
waits
MERINETH IS BACK
FINALLY
WHERE IS MY SLAMS HANDS MATHS
$\int_2^{\infty} \frac{x}{x^4 -1}dx$
hmm
Merineth
My answer is
hang on hang on
i need to evaluate the integral
while absolutely hammered
oh partial fractions? no?
im dum
eh i give up
im horrible at PFD anyways
$\frac14 \ln[x^4-\sqrt{x^4}]$
Merineth
I did not use partial fraction, i used u sub
basically what im tryna say
is that the derivative of that is (x^3 - 0.25 / x^4 - x)
so doesnt seem to be correct
@devout valley lil help
What u did you take?
x^4-1
Ye you need to be a little more clever about it
(or at least not very nicely
)
no it straight up doesn't work
it's 00:16 AM for me rn, i think i'll go in about 3-5 minutes
why did i write AM
it was obvious
see im hammered
I think i forgot to cancel an x in denom
That's just not right
where did u get last step
it doesnt make any sense
please tell me im making sense
i cant tell anymore
waits
can i spoiler a WA request
imma test it
appears not
okay so it doesn;t
@next basalt done? i'd like to finish this b4 i sleep
Hm i tried it again but this time i got $\frac14 \ln|x^2|$ which is most likely wrong
Merineth
Partial fraction seems to be the only way afaik. Thought i could get away by using u substitution
When you're dealing with an x^4, always check if (x^2)^2 is easier to work with
||yes||
So my mistake was taking the entire denominator with u substitution when i should've just taken x^2?
cool ty @queen crater
yep
How in the world do i recognize that i should take x^2 and not x^4 -1?
||i thought about u^2 first but wasn't sure about the later int, thanks for helping||
for nel
You should recognize that the derivative you want should cancel the numerator
always try it
jic
Yes, that i did with x^4
chartbit's still here??
The numerator is x, something that cancels it is x too, so x^2 seems like a good thing to at least try
So the goal is to cancel the numerator but also at the same time make sure we aren't left with something worse after the cancelation? Since we can just factor out 1/2 after u subbing x^2?
yes
Well in general the goal is to get to a form for which you know a formula
but that helps
Here it would be 1/(x^2-1)
in getting to nel's goal
Yes
then factorize
via PFD
my god i cant type
alr guys i think imma b heading out
it's 00:34 (kinda offended you aren't stalking me Merineth, i've announced my time before. hmph)
okay jk, this was honestly a lotta fun
peace
Have a good rest 
yep
If i factor out 1/2
and then i apply partial fraction
do i multiply 1/2 infront of both the integrals?
Yep, you'd need to make sure you apply it to both the integrals you find
hm
I applied partial fraction and got
$-\frac14 \int_2^N \frac{1}{u-1} du + \frac14 \int_2^N \frac{1}{u+1}du$
Merineth
the only way i see what i can do here is u subbing again?
so i get 1/t
Is it okay to sub while it's already subbed?
Is that equivalent to several chains in the chain rule?
you may have the + and - the wrong way around I think
Integral of 1/x is ln(x), so integral of 1/(x+a) is just ln(x+a)
Because the derivative of x+a is the same as the derivative of x
I don't think so? Checking atm
I got A = 1/2 B = -1/2
But what did A and B relate to originally?
the numbers are fine but their order isn't 
$\frac{1}{(u-1)(u+1)} = \frac{A}{(u-1)} + \frac{B}{(u+1)}$
Merineth
That could be because you solved with the
in the other order on the LHS?
This plus A = 1/2 B = -1/2 gives you the other order
$1 = A(u+1) + B(u-1)$
Merineth
We're happy with how you got those values
put them in here: what does it look like?
okay i see what you mean
i forgot to factor out the -?
$\frac14 \int_2^N \frac{1}{u-1} du - \frac14 \int_2^N \frac{1}{u+1}du$
Yea, should have been the other way around, the thing that corresponded to your first term should have been +1/2 and the second term -1/2
Merineth
I despise integrals
one tiny - wrong and gone goes 5 points on the exam
lmao
$\frac14 (ln|x^4-2| - ln|x^4|)$
Merineth
Oh wait a moment actually, forgot you subbed
$\frac14 \ln|u-1| - \frac14 \ln|u+1|$
Merineth
Yeeaaaa not this cause the sub was u = x^2 
Me too tbh 
but yeah u = x^2
I'm gonna just make the excuse that you should have changed the limits and then we could happily have forgotten about the sub 
[similar don't forget to disinguish the limits here that they're wrt x, not u]
@next basalt Has your question been resolved?
time for linear algebra.. :(
How do i determine a planes equation?
If the information i'm given are two lines?
I understand that a plane is
Ax + By + Cz = d
Yes they intersect
It was the question from yesterday but b)
Denote with L1 the line through the points A = (2, −2, 0) and B = (7, −17, 10) and with L2 the line (x, y, z) =
(−3, −7, −14) + t(1, 2, 3), t ∈ R.
a) Show that L1 and L2 have a common point. Which?
b) State the equation for the plane that contains both L1 and L2.
I determined a point (1,1,-2) in a)
Ok so an easy way to find an equation of the form ax+by+cz=d is to find a normal vector and then adjust d
and the normal vector is determined by the cross product between both lines directional vector?
Okay i got the n vector = (65, 5 -25)
Ok, haven't checked, but that gives you a,b,c, now you need to adjust d so that all the points in the two lines are also in the plane
Can i take the dot prodcut between the normal vector i just found and dot it with (r - P) where r and P are two points in the plane?
oh right
Just set up an equation
I mean, pick a point, use the incomplete equation of the plane that you have
It straight up gives you d
oh just put in the cordinates of x y z of a point and solve for d?
Yes
That's the point of the equation of the plane: every point (x,y,z) that is in the plane satisfies the equation
Oki i got d =120
is there a way to verify my plane?
Ooh i can check if the dot product between the normalvector and the plane = 0
Yeah
I'm given a plane, and a line
(a) Determine the point P where the line L and the plane pi intercept
(Sorry if it's bright btw)
But I plugged in the lines equation into the planes equation to find out t, then i took that t into the lines equation and found the point (-3,3,2) seems ok?
Yes
(b) asks me to determine the ortogonal projection of L_1 and L on the plane pi
However they haven't given me the equation for L_1?
So how can i do the cross method
"Enter the orthogonal projection L1 of L onto the plane π."
oh so it's the cross product between the normal vector and L which gives me the vector V_l

The cross product will give you a vector orthogonal to both
It will be orthogonal to L_1 too
My suspicion is that i shall use the projection formula to somehow establish L_1
You can
What's v?
The vector of L
Yeah that works
Read it like a function
The function is called proj_v
So it's the projection of u
The u' indicates that too, it's a new vector that comes from u, it's its projection
I figured out what my lambda is or rather the coefficient before my planes vector
do i just take it not and multiply it into my planes vector?
You lost me
Basically i'm projecting v towards the plane by using the projection formula.
$\frac{v \cdot n}{|n|^2}$
Merineth
Is my lambda = coefficient which i got to be 8/3
multiplied with my planes normal vector
What lambda are you talking about
My teacher says lambda is the coefficient
he says this is "lambda"
Oh okay
Then yes

Then yeah you did it wrong 
$\frac38 (1,-,1,1)$
Merineth
Yea
L_1 is also a projection, as in the projection of L onto pi
The question asks you to find L_1, right?
I'm not sure tbh he is very unclear:
It just says:
"State the ortogonal projection L_1 by L on the plane pi"
- State the ortogonal projection L_1
Is what i see from it at least
It's just how you express a line
Oh so he is just unclear then?
Apart from drawing it
I mean it's not unclear to me, but it could be more clear I guess
I can see that they have a point where L and L_1 cross.
But without the equation of L_1 i don't know how to figure that point out.
.
But that isn't the point where L_1 and L cross each other?
That is when the plane and L cross
L_1 being the projection of L onto the plane, if you take that point on L and project it onto the plane, then it's just the same point
Oh okay you are not looking at the figure correctly
The green point is nothing
OH
The plane is behind the line there
L is upwards away from the plane
Yes
Ahhh i see what you mean
Doesn't that mean L_1 = (x,y,z) = (-3,3,2) +t(8/3, -8/3, 8/3)
No, that's a line orthogonal to the plane
It's the line that goes through the blue point here and goes in the direction of the normal vector
It's getting a bit confusing
You projected L onto the normal vector, so of course you get a line parallel to the normal vector
Kind of
Oh
unless
So i'm trying to find a orthogonal vector
with the normal vector i just got?
No there is an infinite number of those
I see
Ok here are three ways to do it
- do the cross product between v and n to get v2, then do the cross product between v2 and n to get v1
- pick another point on L, for example (2,1,3), project it onto the plane using the normal vector; that means set up an equation where (x,y,z) = (2,1,3) + (1,-1,1)*s and x-y+z=-4, solve for x,y,z; then you have 2 points to define L_1
- directly project v onto the plane, but for that you need to first project it onto n (which you did) to get v3, and then subtract that: v1 = v - v3; L_1 is defined by (-3,3,2) + v1*t
- seems easiest afaik
But how would that look like graphically?
The first time i do the cross product between them, where would it point?
3 is probably easiest, cross products can be a pain
I have a really neat trick for cross product!
I know about Sarrus's rule, it's still a pain sometimes
Nope not sarrus rule afaik
2 x 3 = 3*2-4*1 = -1, 2, -1
3 4 1*3-2*2
-------
1 2
2 3```
for example 
Put all that in code:
` ` `
like this
` ` `
Damn it
without the spaces
That is Sarrus's rule
Oh
Looks a bit different but it's the same thing
So v is (5,-2,1), right?
And n is (1,-1,1)
Works too, just inconvenient
I always forget i can factor out
since the length doesn't matter
for the vector
:)
How it looks graphically:
https://www.desmos.com/3d/5fb7823cb3
L in blue, n in red, v2 in gray, v1 (or L_1) in green
How do i verify my answer?
Graph it 
If you take any point on L, you can get to it starting from (-3,3,2) by adding pv1 and qn, with some scalars p and q (p/q will be constant)
So (-3,3,2) + pv1 + qn = (2,1,3) + (5,-2,1)t, for any t, where p/q is always the same
That's a bit convoluted though
It's just to say that the plane formed by n and v1 (and (-3,3,2)) contains L
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Hey, how do I do this?
I need to do (b)
I'm presuming I need to find smallest $r$ possible such that $(x - 2)^2 + (y + 3)^2 + (z - 6)^2 = r^2$?
∞
For the sphere to be "touching" the yz-plane
Have you done a?
Well you know which axis is perpendicular to yz plane
Yeah, the x-axis
What does this mean?
So imagine you have this $(x - n)^2 + (y + 3)^2 + (z - 6)^2 = r^2$
casework
What can you tell me how the sphere changes its place when you change n
@torn jolt Has your question been resolved?
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Its distance from the yz-plane changes
r = 2?
Yes
Ok, I understand the reasoning behind the answer... now, how would I be able to write it up?
I have this so far as my answer
Got you, thanks a lot
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In a series a_n = (-1)^n +1/n
What would be the limit to this?
Could you have 2 for each signed value? Since 1/n converges to 0 and -1^n oscillates between +1 and -1, meaning that for each even n value, the series converges to 1 and -1 for odd n values, which is like having 2 curves or am i wrong in thinking this way? Also would epsilon have to extend to both -1 up to +1 or is it depending on the nth value?
if a sequence converges, then its limit is unique
One of the properties of convergence
so if by absurd a_n converged...
So in this case it would have 2 unique limits, depending on n being odd or even?
do you know what "unique" means?
it means one
if l1 and l2 are both lim_{n-> infinity}(a_n), then l1 = l2
I do agree that $\lim_{n\to \infty}(a_{2n}) = 1$ and $\lim_{n\to \infty}(a_{2n+1}) = -1$
rafilou2003
but then what would $\lim_{n\to \infty}(a_{n})$ be?
rafilou2003
Idk :c
Thank you for breaking it down like this, i understand now. Is it like the irrational roots of polynomials?
uh no I don't see the connection
it's just that IF the limit existed, then it would either be 1 or -1
Oh sorry, the irrational roots just dont make sense to me, so i thought it might have a connection. I can only find the real ones.
but if it were 1, then the odd terms don't approach the limit (impossible)
Right! This clears it up. Thx a ton! 
and if it were -1, vice versa with even terms
so the limit cannot exist at all
(a_n) diverges
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why do you think b is C(3,1)?
indeed it isn't C(4,1) because you have to choose two more elements
?
In the notation C(n,k), n represents the list of stuff you can choose FROM
if 2, 3, 5 must be included, how many more elements of S can you choose from?
4?
2?
2
2?
yes 2
C(3,2)?
why 3?
you still have to choose 2 elements to complete your subset
how many elements can you choose from?
4
2
7 elements
answer both those in one sentence
"I still have to choose __ elements from a list of __ elements"
2, 3
Why 3?
you still have to choose 2 elements to complete your subset
how many elements can you choose from?
(you answered this question earlier correctly)
4
yes
I think you can attempt this again
2, 4
16?
uh no
Remind me how many possibilities when having a list of n stuff, choosing k of them?
6?
@brittle nebula Has your question been resolved?
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the exponents are confusing me
when multiplying like terms, all you gotta do is add the exponents
then what
it wants me to simplify
i got when i multuplied the square root of 9x^19 * y^6
ye, so you multiply the coefficients (3 in this case), multiply the variables, and then if the number is a perfect square, just square root the number.
as for the variables, I'll gibe you an example:
√(x⁵), if you expand it, it is √((x)(x)(x)(x)(x), you pair the variables, so it'll be x²√x
I'm not the best at explaining, but do you kind of get it..?
yesss, you got it!
yipppee
I'm learning that too, and it's confusing to me as well💀
ok I think i just wasnt simplifying correctly or not at all
ye prob
thank you :)
ofc!
good luck :))
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@torn jolt Has your question been resolved?
That's basically what the instructions did.
@torn jolt Has your question been resolved?
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how would u plot this on an argand diagram
@grim oak Has your question been resolved?
Hmm first of all can you simplify arg(z²)?
no
no
i can
😭😭
but there's a lower boundary and stuff
and that just makes it confusing
dunno what the boundaries r
Okay, in your class, what was the convention for arguments?
wdym convention
Like a circle keeps going round and round you need to agree in where to start and stop
-pi to pi
what
2θ>π/2 means...?
my tutor went through it
but I was like asleep
and I tried to take a photo
and this is all I got but he was considering all these other scenarios
idk
No
Arg(z²) is given in the question to be >π/2
Hence the shaded region for z²
i get that now
Now the shaded region can be referred to with a couple different names
The obvious way to call it is π<θ<π/2
Right?
yes
But if we only consider that we miss out on the full answer
are the grater than symbols other way around
Because squaring does weird stuff where it causes space to double over on itself
Yes I'm sleepy too
So upper left quadrant is π/2<θ<π
But it can also be thought of as -3π/2 < θ < -π
Think about it
Now θ here is arg(z²), ie twice the angle you want
yea
So halve these inequalities/ranges to get...
..
π/4 < θ/2 < π/2
Or
-3π/4 < θ/2 < -π/2
Where θ/2 is arg(z)
Both of these ranges work, right?
can u explain this
Ok so you know how π and -π basically refer to the same angle
yes
Similarly, π/2 is the same as π/2+2π or π/2-2π or really π/2 + any integer multiple of 2π
Cuz going around in a circle any number of times doesn't change anything
yea
Notice we only considered two ways of writing angles here, that's because of the z²
If you were doing a problem with z³, you'd have to consider three different ways to write the range
And if you had z⁴... Well you get the picture
would it b the same as 2pi
Yes, 2π=4π
Basically, any angles that differ by an integer multiple of 2π are equivalent
This really all boils down to how taking a square root gives you two answers
And you need to consider both
Like it's the same thing but at a more general level here
Yeah you need to have seen it before
yea
Only one person in the class got it
in a class of over 150
and my tutor has been teaching since like 2010
Lucky you have practice problems so the test doesn't give any nasty surprises
he said no one ever got it first try before
perfect
ok thanks
.close
Aight cool
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For this question I have to find the arc length s of the vector function r(t) = 7cos^3(t)i + 7cos^3sin(t)j + k from t = 0 to t = pi/2.
I have gotten to the point where I took the derivative and have sqrt((-21cos^2(t)sin(t))^2 + (21sin^2(t)cos(t))^2) but I keep getting stuck from there
Show your entire work
I erased it all I kept getting lost and the answer was wrong
how are we supposed to know what went wrong with what you did then?
Anyways, remember that the arc-length for a vector-valued function in an interval $[a,b]$ is defined as: [
L = \int_a^b \s{\p{\dv[x]t}^2 + \p{\dv[y]t}^2 + \p{\dv[z]t}^2}\dd t
]
Redo it then
Fair point I guess I don't know how to integrate the simplified magnitude. sqrt(441cos^4(t)sin^4(t) + 441sin^4(t)cos^4(t))
Redid it
Redid it
<@&286206848099549185>
@scenic stream Has your question been resolved?
@scenic stream Has your question been resolved?
I got $\frac{21\pi \sqrt{2}}{16}$
Αρχιμήδης
I'll take a look at your working and find the mistake.
How did you go from line 5 to line 6?
$21\sqrt{2} \int cos^2(t) sin^2(t) dt$ = $2^{3/2} \int v^2$
Αρχιμήδης
I'm confused how to take the integral of that stuff
Have you learned integration by parts?
Yeah but it's been a long time since I learned it
Alright. Give me about 5 minutes and I'll write up a quick formula you might need.
Thank you!
Almost done
The last line in the proof is the most important. What I did with the original question was I took cos^2(x) sin^2(x) and rewrote it as:
sin^2 (x) cos^2 (x) = sin^2 (x) (1-sin^2 (x))
This is because cos^2 (x) + sin^2 (x) = 1, cos^2 (x) = 1- sin^2 (x),
Then I took
sin^2 (x)(1-sin^2 (x)) = sin^2(x) - sin^4(x),
Then I used the formula below to integrate the two. There might be a nicer way to do it, but this is the way I've always solved questions like this.
.
\begin{align*}
\int \sin^n(x),dx&=\int \sin^{n-1}(x)\sin(x),dx\\
\text{Using IBP:}\\
\begin{matrix}
u=\sin^{n-1}(x) & dv=\sin(x),dx\
du=\cos(n-1)\sin^{n-2}(x_,dx & v=-\cos(x)
\end{matrix}\\
\Rightarrow \int \sin^n(x),dx&=-\cos(x)sin^{n-1}(x)+(n-1)\int \cos^2(x)\sin^{n-2}(x),dx\\
&=-\cos(x)\sin^{n-1}(x)+(n-1)\int \sin^{n-2}(x)(1-\sin^2(x)),dx\\
&=-\cos(x)sin^{n-1}(x)+(n-1)\int \sin^{n-2}(x),dx - (n-1)\int \sin^n(x),dx\\
n \int \sin^n(x),dx&=-\cos(x)sin^{n-1}(x)+(n-1)\int \sin^{n-2}x,dx\\\
\int \sin^n,dx &= \frac{n-1}{n}\int \sin^{n-2}(x),dx-\frac{cos(x)sin^{x-1}(x)}{n}
\end{align*}
Αρχιμήδης
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
The formula for cos is the same, but you add the fraction on the right instead of minusing it.
I found the mistake in my proof. In the IBP substitution, it should be:
du = (n-1) [sin(x)]^(n-2) cos(x) dx
Thank you so much!
@scenic stream Has your question been resolved?
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can someone explain the highlighted part?
well when k is 0, it's q^0 - 1 which is just 0
so it's like, sum from 1 to infinity is equal to sum from 0 to infinity
because you're just adding 0
$\sum_{k=1}^{\infty} (c\cdot q^k)=c\sum_{k+1}^{\infty} q^k$
SWR
oh god thats still confusing but i appreciate the help
i know constants are allowed to be put in front of the sum
but that infinity rule is a bit too much
so its basically just saying it doesnt matter if k starts from 1 to infinity or k+1 to infinity? because its both going infinitely long?
Kaisheng21
yeah
was just wondering how they got k to be 0 by subtracting c
they do it quite often in this answer sheet if thats something i can just do i guess ill learn it? but it doesnt make sense to me
$\sum_{k=0}^{\infty} (q^k - 1) = (q^0 - 1) + \sum_{k=1}^{\infty} (q^k - 1) = 0 + \sum_{k=1}^{\infty} (q^k - 1) = \sum_{k=1}^{\infty} (q^k - 1)$
Kaisheng21
so it's just because the k = 0 term is 0
yeah
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Please help : For how many pairs of positive integers (a, b) do we have minimum comun multiple (a, b) = 2024
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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
@vague panther Has your question been resolved?
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how do u derive sin2x/cos2x
the 'worked' answer is very useful
solution has a typo
where at
the dy/dx
is it just 2/cos(x) not squared
show what you did
$(2(cos^2(2x) - sin^2(2x)))/cos^2(2x)$
™Vlad The Lad
bomboclat
you messed up some signs
cuz before innit
(2cos(2x)cos(2x) - 2sin(2x)sin(2x))/cos^2(2x) (straight form quotent)
-2sin(2x)?
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$\lim_{{x \to 3}} \left( \left| x - 4 \right| \right)^{\frac{1}{\left| x - 3 \right|}}$
Alex
Find the left and right limits.
im not sure how to handle this
does the limit changes depending the side? I assumed kt wiuld be the same because of absolute value
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for this since you know they intersect, just find normal and solve system right
i did it but my answer looks kinda wrong.
@torn jolt Has your question been resolved?
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How do I find all pairs of numbers with minimum comun divisor=2024
are you sure you meant to write "minimum common divisor" there
Yes
