Let $f ( x ) = \tan ^ { - 1 } ( \cot x )$

Multiple Choice

Let $f ( x ) = \tan ^ { - 1 } ( \cot x )$ Then $f ^ { \prime } ( x )$ is

A) -1
B) $\frac { \sec ^ { 2 } x } { 1 + \cot ^ { 2 } x }$
C) $- \frac { \sec ^ { 2 } x } { 1 + \cot ^ { 2 } x }$
D) 1
E) $\frac { \cos ^ { 2 } x } { 1 + \cot ^ { 2 } x }$