What is the derivative of f(x)=arctan(sinh(x))f(x) = \arctan(\sinh(x))f(x)=arctan(sinh(x))?
sech(x)\text{sech}(x)sech(x)
1cosh(x)\frac{1}{\cosh(x)}cosh(x)1
cosh(x)1+sinh2(x)\frac{\cosh(x)}{1+\sinh^2(x)}1+sinh2(x)cosh(x)
11+x2\frac{1}{1+x^2}1+x21