# Infinite integral

1. Sep 23, 2008

### kasse

Working with Fourier integrals, I need to find the integral

$$\int cos (wv) dv$$ between -$$\infty$$ and $$\infty$$. Is it possible to find this integral?

What I get is sin(wv)/(pi*w) with the infinite limits for v.

2. Sep 23, 2008

### Dick

Where did the pi come from? In the sense of a ordinary integral it makes no sense, it's divergent. In the sense of a fourier integral it can make some sense, if you are also integrating over w. But I think you need to give us the complete context.

3. Sep 24, 2008

### HallsofIvy

Staff Emeritus
If you are working with Fourier series, why are you integrating from negative infinity to infinity? The integral should be over one period.

If you are working with the Fourier transform, why are you integrating cosine? Write everything in terms of exponentials: cos(wv)= (ewv+ e-wv)/2.

As Dick said, please give us the entire problem.