The argument of a complex number complex(x,y) on the complex plane:

When a complex number is written in polar form

*x* + *iy* = *r e ^{iφ}*

then its argument is the real value *φ* in the exponent. It is calculated numerically using the atan2 function.

This example deliberately replicates some of the arithmetic of complex numbers of Math to avoid importing that entire library for a couple lines of code. It also encodes the tiny amount of mathematical notation in HTML to void importing all of MathJax.

Complete code for this example: