Chapter 7.6, Problem 13AYU

In Problems $9-20,$ use the information given about the angle $\theta ,0\le \theta <2\pi ,$ to find the exact value of:

$(a)\sin (2\theta )(b)\cos (2\theta )(c)\sin \frac{\theta }{2}(d)\cos \frac{\theta }{2}$

$\cos \theta =-\frac{\sqrt{6}}{3},\frac{\pi }{2}<\theta <\pi$