Double Angles

cos2u =

Use a double-angle or half-angle identity to find the exact value of each expression

cos θ = 4/5 and 270° < θ < 360°Find sin 2θ

If cosx = - 4/5, find secx.

 $Given\ \cos\theta=\frac{5}{13}\ and\ \frac{3\pi}{2}<\theta<2\pi\ find\ \sin2\theta$  

Given that $\sin\theta=\frac{3}{7}\ where\ \frac{\pi}{2}<\theta<\pi,\ \ find\ \cos2\theta$  

 $Given\ \cos x=\frac{5}{13\ }\ where\ x\ is\ in\ Quadrant\ 1,\ find\ \tan2\theta$  

 $Given\ \sin\alpha=\frac{3}{7}\ and\ \theta\ is\ in\ Quadrant\ 2,\ find\ \sin2\theta$  

 $Given\ \sin\beta=-\frac{5}{8}\ where\ 270\degree<\beta<360\degree,\ find\ \tan2\beta$