Rotate the figure 90 degrees about vertex A.

A' is (1,1) B is (4,1) C is (1,-1)

Step-by-step explanation:

Since we rotating the figure about point a, we know a is the center of the rotation meaning no matter how far we rotate point a new image will stay on where point a pre image was which in this case is (1,1). Also since we know the rules of rotating a angle 90 degrees About the origin we are going to translate the figure to have the one point we are rotating about at the orgin. Since translations are a rigid transformations, the figure will stay the same A. Move the figure 1 to the left and 1 down so A becomes 0,0 B becomes 0,3 and C becomes 2,0. Then apply the rules of 90 degree clockwise rotation rules. (x,y) goes to (y,-x) . A stays (0,0) B becomes (3,0) and C becomes (0,-2). Then translate the figure 1 to the right and 1 down since we rotating about point a which is 1,1 and it at 0,0 rn. A' is 1,1. B' becomes (4,1). C' becomes (1,-1).