De Moivre's formula 棣莫弗公式
(重定向自DeMoivre formula)
In mathematics, de Moivre's formula (also known as de Moivre's theorem and de Moivre's identity), named after Abraham de Moivre, states that for any complex number (and, in particular, for any real number) x and integer n it holds that
where i is the imaginary unit (i = −1). While the formula was named after de Moivre, he never stated it in his works. The expression cos x + i sin x is sometimes abbreviated to cis x.