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.


Example
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`.