# When to use fourier integral instead of fourier series expansion

1. Jan 13, 2012

### Naughty Boy

Suppose, I have a non-periodic signal for which amplitude spectrum is to be obtained . For this why should fourier integral be used instead of fourier series expansion . I want to know when to use fourier inerals and when to use fourier series . Please let me know all the details .

2. Jan 14, 2012

### Gordianus

If memory serves Fourier integral applies to square integrable functions and, with the use of Dirac delta function, to periodic functions like sine and cosine. The Fourier series expansion applies to periodic functions.

3. Jan 14, 2012

### maverick_starstrider

You use fourier series if the function is periodic, transforms if it's not.