# Fourier series pleeeease

fourier series pleeeease :(

Hi every one,

Actually it seems simple but I could not answer them because I did not understand the lesson very well.

This homework worths 5% and I have to hand it as soon as possible!

Find the fourier series expansion for the function over the specified intervals:-

1- f(x)= 1, -∏< x < ∏

2- f(x)= 0, -∏< x < 0 and x^2, 0< x < ∏

Find fourier cosine series:-

- f(x)= x, 0< x < ∏

Find fourier sine series:-

- f(x)= -x, 0< x < 1

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malawi_glenn
Homework Helper
yes, but you have to show attempt to solution and what relations you know of dude. Otherwise you can't get help. It is agaist the forum rules.

If you do this, write the relations you know of, and at least a start from your side. Then I'll kick you in the right direction.

Thank you for telling me.

Actually I started by finding a(0) and a(n) and b(n)

my attempt for the first question

a(n)= I think 0

b(n)= ((-1)^n-(-1)^n)/(n) which is I am really not sure about

And if I get these three answers, should I only substitute it in the main equation OR I have to go in further steps?!

Thank you again my dear

Defennder
Homework Helper
How did you get 2?

To find a(n) and b(n), note that f(x) is an even function. So what does that tell you about a(n) and b(n)?

Once you get a(n) and b(n) just substitute them into the expression for the Fourier series.