Use the Given Information to Compute $\cos \left( \frac { \theta } { 2 } \right)$

Multiple Choice

Use the given information to compute $\cos \left( \frac { \theta } { 2 } \right)$ . $\cos \theta = \frac { 4 } { 7 }$ and $\frac { 3 \pi } { 2 } < \theta < 2 \pi$

A) $- \frac { 14 } { 15 }$
B) $- \frac { \sqrt { 154 } } { 14 }$
C) $\frac { \sqrt { 143 } } { 14 }$
D) 4/15
E) $\frac { \sqrt { 77 } } { 15 }$