Hi all,

I'm stuck with just one step now of a long problem.

Basically, how do I get from

$\displaystyle (1+2sinx)(\frac{1}{2}-sinx)$

to

$\displaystyle 2cos(x)^{2}-\frac{3}{2}$

I've been told I need to use just one trigonometric identity, but I honestly can't think of any that will do it?

Many thanks.