How Do You Calculate Fourier Series for Functions Like sin(nπ)?

[KAS90]

Homework Statement

find Fourier series for:
sinnπ=0
(n=0,+1,-1,+2,-2...)

I really can't understand how Fourier series works.. Like I tried solving problems..but till now, it didn't sink in my brain..
I just want 2 know the basic way of solving a problem regarding Fourier series..then it will be much easier to understand I guess..
Thanx in advance..

 

[Mark44]

Homework Statement

find Fourier series for:
sinnπ=0
(n=0,+1,-1,+2,-2...)

I really can't understand how Fourier series works.. Like I tried solving problems..but till now, it didn't sink in my brain..
I just want 2 know the basic way of solving a problem regarding Fourier series..then it will be much easier to understand I guess..
Thanx in advance..

What's the function that you want to find the Fourier series for? sin (n*pi) = 0 for all integers, as you point out, but it's otherwise not very interesting. Is the function f(x) = 0?
If so, all of the coefficients in the Fourier series would be 0.

Is there more to this problem that you haven't shown us?

 

[KAS90]

What's the function that you want to find the Fourier series for? sin (n*pi) = 0 for all integers, as you point out, but it's otherwise not very interesting. Is the function f(x) = 0?
If so, all of the coefficients in the Fourier series would be 0.

Is there more to this problem that you haven't shown us?

hi mark
sorry 4 being late..plus giving a completely wrong question..
ok..
the I realize the problem is for example :
f(x)= sinx
0<x<pi
it's a problem I want to understand like how is it really solved?

 

[HallsofIvy]

A Fourier series for a function f(x) is an infinite sum such that
f(x)= \sum_{m=0}^\infty A_n cos(nx)+ B_n sin(nx) (or other (x/L) or whatever inside the trig functions).

Of course, the right side of that is periodic with period 2\pi so if f is not itself periodic, that can only be true on some interval (which is one reason why you might need that "/L" to alter the interval).

But if f(x)= sin(x) is not only periodic with period 2\pi, it is already of that form and it is obvious that A_n= 0 for all n, while B_1= 1 and B_n= 0 for all n greater than 1.

More generally, if f(x) is integrable on the interval [0, L], then on that interval f(x)= A_n cos(2n x\pi/L)+ B_n sin(2n x\pi/L) where
A_0= \frac{1}{L}\int_0^L f(x) dx
A_n= \frac{1}{2L}\int_0^L f(x)cos(2n x/L)
for n> 0 and
B_n= \frac{1}{2L}\int_0^L f(x)sin(2n x/L).

 

[KAS90]

A Fourier series for a function f(x) is an infinite sum such that
f(x)= \sum_{m=0}^\infty A_n cos(nx)+ B_n sin(nx) (or other (x/L) or whatever inside the trig functions).

Of course, the right side of that is periodic with period 2\pi so if f is not itself periodic, that can only be true on some interval (which is one reason why you might need that "/L" to alter the interval).

But if f(x)= sin(x) is not only periodic with period 2\pi, it is already of that form and it is obvious that A_n= 0 for all n, while B_1= 1 and B_n= 0 for all n greater than 1.

More generally, if f(x) is integrable on the interval [0, L], then on that interval f(x)= A_n cos(2n x\pi/L)+ B_n sin(2n x\pi/L) where
A_0= \frac{1}{L}\int_0^L f(x) dx
A_n= \frac{1}{2L}\int_0^L f(x)cos(2n x/L)
for n> 0 and
B_n= \frac{1}{2L}\int_0^L f(x)sin(2n x/L).

THANX a lot Hallsofivy..
u were a lot of help..as usual lol..