I recently came across two identities for the derivatives of the Bessel functios $J_n,Y_n$, namely $$\begin{align*} J_n'(z) = \frac{J_{n-1}(z)-J_{n+1}(z)}{2} && Y_n'(z) = \frac{Y_{n-1}(z)-Y_{n+1}(z)}{2}\end{align*}$$ However I cannot find these identities anywhere in the literature. Does anyone...