Meaning of de Moivre's theorem

de Moi'vre's the'orem

Pronunciation: [key]
— Math. Math.
  1. the theorem that a complex number raised to a given positive integral power is equal to the modulus of the number raised to the power and multiplied by the amplitude times the given power.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.