Polygon abcd is rotated 90º counterclockwise about the origin to create polygon a′b′c′d′. match each set of coordinates to the vertices of polygon a′b′c′d′. tiles a′ (-1, 3) b′ (-2, 2) c′ (-2, 1) d′ (-1, 1)

Rules for rotating points about the origin
 1. The point (a,b) rotated 90° counterclockwise about the origin
becomes (-b,a).
A′ (-1, 3) B′ (-2, 2) C′ (-2, 1) D′ (-1, 1)
A (a,b)A′ (-b,a)=(-1, 3)>A( 3,1)
B (a,b)B′ (-b,a)=(-2, 2)>B( 2,2)
C (a,b)C′ (-b,a)=(-2, 1)>C( 1,2)
D (a,b)D′ (-b,a)=(-1, 1)>D( 1,1)