# What is De-Moivres theorem in complex numbers ?

 De Moivre’s Theorem :It is a formulauseful for findingpowersandrootsofcomplex numbers.$(\cos x + i \sin x)^n = \cos (nx) + i \sin (nx).\,$Say, given a complex number z, and you have to find its cube. Dont use the usual method to multiply z three times. It becomes easier from De moivre's theorem.z^3 = r^3 ( cosx + sinx)^3 = r^3 ( cos3x + sin3x)ThanksBharat BajajIIT Delhiaskiitians faculty