Hypergeometric sine identity
= Hypergeometric sine identity
For $k\ne0$ and compatible local branches near $x=0$,
$$
F\left(\frac{1+k}{2},\frac{1-k}{2};\frac32;\sin^2x\right)
=\frac{\sin(kx)}{k\sin x}.
$$
This is obtained from the <second local hypergeometric solution> at zero and its normalization.