Look at the following rectangle drawn on the x and y-coordinate axes.
When we rotate a shape about a centre of rotation, we also need to know the angle of the rotation and the direction.
In this example, the rotation will be 90º clockwise.
This is done by moving each point around the centre of rotation, which in this case is at A.
The result looks like this:
Notice that A and A' are at the same point and have not moved.