How to rotate a 2D point #219

In 2-D, the 2 × 2 matrix is very simple. If you want to rotate a column vector v by t degrees using matrix M, use

M = {{cos t, -sin t}, {sin t, cos t}}

in M * v.

If you have a row vector, use the transpose of M (turn rows into columns and vice versa). If you want to combine rotations, in 2-D you can just add their angles, but in higher dimensions you must multiply their matrices.

Original resource:	The Delphi Pool
Author:	Joseph O'Rourke
Added:	2013/04/09
Last updated:	2013/04/09