Let $f ( x ) = \ln ( \tanh x )$

Multiple Choice

Let $f ( x ) = \ln ( \tanh x )$ Then $f ^ { \prime } ( x )$ is

A) $\operatorname { csch } x \operatorname { sech } x$
B) $\sinh x \cosh x$
C) $\operatorname { sech } ^ { 2 } x$
D) $\operatorname { coth } ^ { 2 } x$
E) $\operatorname { csch } ^ { 2 } x$