in reply to Re^2: Rotate a 3D vector
in thread Rotate a 3D vector

just want to point out it's not quite right. You need to first find the polar angle for the original point (x,y), then add the $angle to that for the new polar angle.

Updated. I'm only refering to the geometric meaning. There is a formula: multiplying by the rotation matrix given by ((cos, -sin),(sin, cos)) (not perl notation!)