Answer
$f'(x)=cos^2(x)-sin^2(x)$
Work Step by Step
Product Rule: $f'(x)=u(x)v'(x)+v(x)u'(x)$
$f(x)=sin(x)cos(x)$
$u(x)=sin(x)$
$v(x)=cos(x)$
$f'(x)=(sin(x)\times[-sin(x)])+(cos(x)\times[cos(x)])$
$f'(x)=(-sin(x))^2+(cos(x))^2$
$f'(x)=cos^2(x)-sin^2(x)$
