Question

the point p (-1,2) is rotated to become p (2,1). describe the rotation by degree and direction.

Explanation:

Step1: Recall rotation rules

For a rotation of 90 - degree counter - clockwise about the origin, the transformation rule for a point $(x,y)$ is $(-y,x)$. For a 90 - degree clockwise rotation about the origin, the rule is $(y, - x)$.

Step2: Check rotation rules

Given point $P(-1,2)$ and $P'(2,1)$. If we consider a 90 - degree counter - clockwise rotation about the origin, applying the rule $(-y,x)$ to $P(-1,2)$ gives $(-2,-1)$ which is incorrect. If we consider a 90 - degree clockwise rotation about the origin, applying the rule $(y,-x)$ to $P(-1,2)$ gives $(2,1)$ which is $P'$.

Answer:

90 - degree clockwise rotation about the origin.