To rotate a figure 90 degrees counterclockwise about the origin, each point of the figure has to be changed from (x, y) to (-y, x) . Here are the rotation rules for the most common rotations on a coordinate grid, assuming the origin (0,0) as the center of rotation:

• 90° clockwise rotation: (x,y) becomes (y,-x)
• 90° counterclockwise rotation: (x,y) becomes (-y,x)
• 180° clockwise and counterclockwise rotation: (x, y) becomes (-x,-y)
• 270° clockwise rotation: (x,y) becomes (-y,x)
• 270° counterclockwise rotation: (x,y) becomes (y,-x)

To perform a 90-degree counterclockwise rotation, each point of the figure has to be changed from (x, y) to (-y, x) .