This page, from Cut the Not, presents a proof using Euler's formula. Following the proof, users have added their own comments and questions. There is also a list of further resources on complex numbers online.

Materials for Precalculus, Differential Calculus, Integral Calculus, Multivariable Calculus, Differential Equations, Linear Algebra, and Engineering Math, with application areas in biology, chemistry, economics,...

This is an introduction to Gaussian primes, complex numbers with integers for real and imaginary parts that are divisible by themselves and 1, but no other complex numbers with integer coefficients. This shows...

If you're a mathematics educator, you'll find the GeoGebra site to be a perfect addition to your stable of online resources. On the top of the homepage, visitors can look through sections that include About, Download,...

Assignments and readings: a resource for mathematics students and teachers, particularly in the areas of Algebra II, AP Statistics, and Statistics/Finance. See also Smith's Writings and reflections.