Question

which of the following mapping is used for a 270 degree (counterclockwise) rotation? (1 point)
(x, y)→(y, - x)
(x, y)→(-y, x)
(x, y)→(-y, - x)
(x, y)→(-x, - y)

Explanation:

Step1: Recall rotation rules

In a 2 - D coordinate system, for a 270 - degree counter - clockwise rotation of a point $(x,y)$ about the origin, we can use the general rotation matrix or memorize the transformation rules. A 270 - degree counter - clockwise rotation is equivalent to a 90 - degree clockwise rotation. The rule for a 90 - degree clockwise rotation of a point $(x,y)$ about the origin is $(x,y)\to(y, - x)$.

Answer:

$(x,y)\to(y, - x)$