9.4 Three Common Rotations about the Origin 

Rotations of 90, 180, and 270 degrees about the origin.
High School Geometry
Three rotations of the same pre-image/ coordinate rules & graphing
90 degrees. (a,b) to (-b,a)
180 degrees. (a,b) to (-a,-b)
270 degrees. (a,b) to (b,-a)