Triangle Rotation COUNTERCLOCKWISE

The slider controls of the angle of rotation of triangle ABC around the origin, which is A'B'C'.[br][br]Move the slider to see how the triangle rotates.
1) What are the coordinates of A', B', and C' when r = 90º?[br][br]2) What are the coordinates of A',B', and C' when r = 180º?[br][br]3) What are the coordinates of A',B', and C' when r = 270º?[br][br]4) What are the coordinates of A',B', and C' when r = 360º?[br][br]5) What patterns do you recognize to transform A to A' for each of these transformations?
– James Baxter, Ben Dougherty

Information: Triangle Rotation COUNTERCLOCKWISE