Rotations
A rotation is a transformation in a plane that turns every point of a preimage through a specified angle and direction about a fixed point. The fixed point is called the center of rotation . The amount of rotation is called the angle of rotation and it is measured in degrees. Use a protractor to measure the specified angle counterclockwise.
Some simple rotations can be performed easily in the coordinate plane using the rules below.
Rotation by 90° about the origin:
The rule for a rotation by 90° about the origin is (x,y)→(−y,x)
Rotation by 180° about the origin:
The rule for a rotation by 180° about the origin is (x,y)→(−x,−y)
Rotation by 270° about the origin:
The rule for a rotation by 270° about the origin is (x,y)→(y,−x)
