How do we graph rotations?

 A rotation is a transformation that turns the figure around the fixed point or the origin . When you want to rotate and don't want to use the entire word rotation you can just write capital R then degrees in the lower right bottom of the letter R. 
Remember: 
R is for rotation (ex: R90) &
r is for reflection (ex: ry-axis)
Rotation rules:
90 degrees = (x,y) --- (-y,x)
180 degrees = (x,y) --- (-x,-y)
270 degrees = (x,y) --- (-y.x)

• Rotation by 90° about the origin: R_{(origin, 90°)}

  A rotation by 90° about the origin can be seen in the picture below in which A is rotated to its image A'. The general rule for a rotation by 90° about the origin is (A,B) (-B, A)

2) Rotation by 180° about the origin: R_{(origin, 180°)}

A rotation by 180° about the origin can be seen in the picture below in which A is rotated to its image A'. The general rule for a rotation by 180° about the origin is (A,B) (-A, -B)

3) Rotation by 270° about the origin: R_{(origin, 270°)}

A rotation by 270° about the origin can be seen in the picture below in which A is rotated to its image A'. The general rule for a rotation by 270° about the origin is (A,B) (B, -A)

http://www.mathwarehouse.com/transformations/rotations-in-math.php