Find the integral of (x cos(2x)) dx, using integration by parts.

I used x as dv/dx and cos(2x) as u.

So v = (v^2/2) and (du/dx) = -2sin(2x)

I am having problems using the formula:

I = uv - Integral ( u' v ) dx. Can anyone help me with this as I can't get the correct answer.