If the point is the centre of rotation, where is the image of ,
is the image of , and cm,
find the measure of the angle of rotation and the length of .
Step 1: Find the angle of rotation.
and are parallel to each other.
and are alternate interior angles formed by a line intersecting two parallel lines, so they are equal in measure: .
To find the measure of the angle of rotation (in the clockwise direction) add .
Step 2: Find the length of .
The side lengths of a rotated image are the same as the corresponding side lengths of the original figure.
is the image of by rotation. Therefore,