TanhExp関数
d d x x tanh  ( e x ) = tanh  ( e x ) + x e x 1 cosh 2  ( e x ) {\displaystyle {\dfrac {d}{dx}}x\tanh(e^{x})=\tanh(e^{x})+xe^{x}{\dfrac {1}{\cosh ^{2}(e^{x})}}}