# Exponential integration confused

## Main Question or Discussion Point

Hi, does anyone know how to integrate e^-x (sin(nπx))? I have tried part integration but that goes on until infinity.... and I am not sure how to use the substitution method....Please help! I have tried taking e^-x as U but then I end up getting the entire cancelled off then...

Simon Bridge
Do you mean: $$\int e^{-x}\sin n\pi x\; dx$$
The trick is this: put $$I = \int e^{-x}\sin n\pi x\; dx$$ ... integrate the RHS by parts, twice only.