# Sin and cos

1. Mar 14, 2009

### chota

if i have to find the integral of

sin(n*pi*x/L) * cos(m*pi*x/L) between 0<=x<=L

is it true that this integral will be 0 every where except where n=m?

$$sin(u)cos(v)=\frac{1}{2}\left[sin(u+v)+sin(u-v)\right]$$