If y= (e^ m x +e^ -m x ) , then what is (d y)/(d x) at x=0 equal to?

y=\log _e\left(e^{m x}+e^{-m x}\right)\frac{d y}{d x}=\frac{1}{\left(e^{m x}+e^{-m x}\right)} \cdot\left(e^{m x} \cdot m+e^{-m x}(-m)\right)=\frac{1}{\left(e^{m x}+e^{-m x}\right)}\left(e^{m x}-e^{-m x}\right)\left(\frac{d y}{d x}\right)_{x=0}=0