Question

a triangle is rotated 90° about the origin. which rule describes the transformation?
$(x, y) \to (y, -x)$
$(x, y) \to (-x, -y)$
$(x, y) \to (-y, -x)$
$(x, y) \to (-y, x)$

Explanation:

A 90° counterclockwise rotation about the origin maps (x, y) to (-y, x).

Answer:

(x, y) → (-y, x)