Find the Derivative Of $y = \tanh ( 7 x )$

Multiple Choice

Find the derivative of $y = \tanh ( 7 x )$ .

A) $\frac { 7 } { \cosh ^ { 2 } ( 7 x ) }$
B) $- \frac { 7 } { \cosh ^ { 2 } ( 7 x ) }$
C) $\frac { 7 \left( \cosh ^ { 2 } ( 7 x ) + \sinh ^ { 2 } ( 7 x ) \right) } { \cosh ^ { 2 } ( 7 x ) }$
D) $- \frac { 7 \left( \cosh ^ { 2 } ( 7 x ) + \sinh ^ { 2 } ( 7 x ) \right) } { \cosh ^ { 2 } ( 7 x ) }$