Atan2
From QED
atan2, a function of C and other sensible languages (but not mainstream mathematics?!?) is a sensible version of the arctangent tan − 1 which doesn't mess up the quadrant at inopportune times. It is defined as φ in the solution to
This page was recovered in October 2009 from the Plasmagicians page on Atan2 dated 21:46, 25 October 2006.