Solve the Problem $\cos \frac { \theta } { 2 }$

Multiple Choice

Solve the problem.
-Find $\cos \frac { \theta } { 2 }$ , given that $\cos \theta = - \frac { 3 } { 5 }$ and $\theta$ terminates in $90 ^ { \circ } < \theta < 180 ^ { \circ }$ .

A) $- \frac { \sqrt { 5 } } { 5 }$

B) $\frac { \sqrt { 30 } } { 10 }$

C) $\frac { \sqrt { 5 } } { 5 }$

D) $- \frac { \sqrt { 30 } } { 10 }$