# Calculating angle of a rotation for a line

by nancy189
Tags: rotation
 P: 455 Calculating angle of a rotation for a line If I understand you right, this is much simpler than you think. If you have a line segment from (0,0) to (x,y) and you rotate it about the (0,0) end so that it's horizontal, you will always end up with (l,0) as the new distal endpoint, where $l=\sqrt{x^2+y^2}$ is the length of the line segment. There's no need to compute the angle of rotation at all.