Explanation:
In order to rotate a coordinate point by 90° in the counterclockwise direction, follow the following transformation rule:
(x, y) ---> (-y, x)
Here is the list of the coordinates of the points on the fan blade and next to it is a list of points that are rotated by 90° in the counterclockwise direction:
Normal. Rotated
(x, y) (-y, x)
(3, 1) (-1, 3)
(5, 2) (-2, 5)
(8, 4) (-4, 8)
(9, 6) (-6, 9)
(8, 8) (-8, 8)
(6, 9) (-9, 6)
(4, 8) (-8, 4)
(2, 5) (-5, 2)
(1, 3) (-3, 1)
Simply repeat the pattern for the other two blades.