National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Derivation of De Moivre's Formula
A formula using Euler's formula to derive DeMoivre's theorem. Basic calculus skills of differentiating and integrating are required to understand this explanation.
Math Medics
S.o.s. Math: The Polar Form of a Complex Number
This lesson from S.O.S. Math provides great information on the polar form of a complex numbers. It has many formulas and examples, and it also discusses the polar coordinates as well. Links are provided for additional subjects.