The figure and its image under rotation about the point O. Rotation by 40°. Rotation by 50°. Rotation by -60°. Rotation by -110°. Rotation in xy-plane. The point A = (x,y) rotated around origin by α is the point A' = (x',y'). x' = x*cosα - y*sinα; y' = x*sinα + y*cosα. Examples. Derivative.