Question

question 12
which mapping represents a rotation of 270 degree clockwise about the origin?
(x, y)→(x, -y)
(x, y)→(-y, -x)
none of the other answers are correct
(x, y)→(-x, y)
(x, y)→(-y, x)

Explanation:

Step1: Recall rotation rule

A 270 - degree clockwise rotation about the origin has the transformation rule $(x,y)\to(y, - x)$. Another way to think about it is that a 270 - degree clockwise rotation is equivalent to a 90 - degree counter - clockwise rotation. The rule for a 90 - degree counter - clockwise rotation about the origin is $(x,y)\to(-y,x)$.

Answer:

$(x,y)\to(-y,x)$ (corresponding to the last option in the multiple - choice list)