Rotation - think pencil compass
On any mathematical rotation think
Rotation - Pencil compass
And with any rotation a pencil compass would need a centre, the direction to move (clockwise or anticlockwise) and the number of degrees to move.
Below is an example of a triangle (`W`). Rotate this triangle 90° clockwise with the centre of rotation being at the origin of the graph (0,0).
Rotate point "`a`" first.
Now rotate point "`b`"
Finally rotate point "`c`"
Triangle `W` rotated 90° clockwise from (0,0)`=W^1`.