The formula

sinz = 1 2p (eiz - e-iz)

can be verified by showing that the series expansion for sinz, that is

sinz = z - z3/3! + z5/5! - z7/7! + ...

can be obtained using the series expansions

eiz = 1 + iz + (iz)2/2! + ...

and

e-iz = 1 -iz + (iz)2/2! + ...