how do we graph rotation?

We graph rotation by 90 degrees , 180 degrees and 270 degrees.

*In 90 degrees
 (a-b)----> (-b,a)
  ex.(2,5)--->(-5,2)

*In 180degrees
   (a-b)--->(-a,-b)
   ex.(5,2)--->(-5,-2)

*In 270 degrees
   (a,b)----> (b,-a)
   ex.(2,5)--->(5,-2)