Clark University
Clark University: Dave's Short Trig Course: Complex Numbers: Absolute Value
Contains detailed information on absolute values for complex numbers.
Khan Academy
Khan Academy: Distance of Complex Numbers
Given two complex numbers (either algebraically or graphically), find their distance. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
CK-12 Foundation
Ck 12: Polar Form of a Complex Number
[Free Registration/Login may be required to access all resource tools.] Here you will learn how to convert complex numbers from rectangular form to polar form. You will also explore the graphs of complex numbers on a polar graph.