# How to take sin^2 out and leave theta

1. Apr 29, 2015

### shanepitts

This is a small portion of a bigger physics problem I am trying to solve, but I can't get passed this little integrand reformulation.

How does this

∫(sinθ/cosθ)d(sin2θ)

Become

∫[sinθ(2sinθcosθ)/cosθ]dθ

Basically, how is the sin2 taken out of the d(sin2θ) and the θ left in the dθ?

Thanks

2. Apr 29, 2015

### Dick

$d(f(\theta))=\frac{df(\theta)}{d\theta} d\theta$. Is that enough?

3. Apr 29, 2015

### shanepitts

It is more than enough

Thanks