theorem :: DIFF_2:61

for x0, x1 being Real holds [!((sin (#) sin) (#) cos),x0,x1!] = - (((1 / 2) * (((sin ((3 * (x1 + x0)) / 2)) * (sin ((3 * (x1 - x0)) / 2))) + ((sin ((x0 + x1) / 2)) * (sin ((x0 - x1) / 2))))) / (x0 - x1))