Without Using a Calculator, Give the Exact Trigonometric Function Value $\tan 45 ^ { \circ }$

Multiple Choice

Without using a calculator, give the exact trigonometric function value with rational denominator.
- $\tan 45 ^ { \circ }$

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