Integrate - Solve \int3^x\cos x\,dx w/ Partial Integration

[Government$]

Homework Statement

Integrate $\int3^x\cos x\,dx$

The Attempt at a Solution

It has to be done using partial integration.

I don't know what should be u?

 

[pongo38]

What choices do you have?

 

[vela]

You're just going to have to try stuff out and see how it works out.