Solve the Problem $f ( \theta ) = \cot \theta$ And $f ( a ) = - 6$

Multiple Choice

Solve the problem.
-If $f ( \theta ) = \cot \theta$ and $f ( a ) = - 6$ , find the exact value of $f ( - a )$ .

A) $- 6$
B) $\frac { 1 } { 6 }$
C) $- \frac { 1 } { 6 }$
D) 6