Evaluate Without Using a Calculator, Leaving the Answers in Exact $\cos \frac { 2 \pi } { 3 }$

Multiple Choice

Evaluate without using a calculator, leaving the answers in exact form. $\cos \frac { 2 \pi } { 3 }$

A) $\frac { \sqrt { 3 } } { 2 }$
B) $\frac { \sqrt { 2 } } { 2 }$
C) 1
D) $\frac { 1 } { 2 }$
E) $- \frac { 1 } { 2 }$