Without Using a Calculator, Give the Exact Trigonometric Function Value $\cos 30 ^ { \circ }$

Multiple Choice

Without using a calculator, give the exact trigonometric function value with rational denominator.
- $\cos 30 ^ { \circ }$

A) $\sqrt { 3 }$

B) $\frac { 1 } { 2 }$

C) $\frac { \sqrt { 3 } } { 2 }$

D) $\frac { \sqrt { 2 } } { 2 }$