Complex Analysis Video #4 (Complex Arithmetic, Part 4). Complex Addition and the Parallelogram Law. Intro to the Triangle Inequality and use of "Manipulate" on Mathematica.
More detail: Geometric interpretation of complex number addition in terms of vector addition (both in terms of the parallelogram law and in terms of triangles). Emphasize that complex numbers can either be thought of as points or as vectors. Triangle inequality verbally described based on the picture. Introduction to the Mathematica command "Manipulate" to make an animation to illustrate complex number/vector addition when the real part of one of the addends changes.