Question

Triangle XYZ has vertices X(1, 3), Y(0, 0), and Z(–1, 2). The image of triangle XYZ after a rotation has vertices
X'(–3, 1), Y'(0, 0), and Z'(–2, –1). Which rule describes the transformation?

R0, 90°
R0, 180°

Answer 1

R about the origin by 90° counterclockwise.

Rule: (x,y) -> (−y, x).

Check: (1,3) -> (−3,1), (0,0) -> (0,0), (−1,2) -> (−2,−1).