Question

the point p (-1,2) is rotated to become p (2,1). describe the rotation by degree and direction. (1 point)
-270° rotation
90° rotation
-90° rotation
180° rotation

Explanation:

Step1: Recall rotation rules

For a point $(x,y)$ rotated about the origin:
A $90^{\circ}$ counter - clockwise rotation gives $(-y,x)$.
A $- 90^{\circ}$ (or $270^{\circ}$ counter - clockwise) rotation gives $(y,-x)$.
A $180^{\circ}$ rotation gives $(-x,-y)$.

Step2: Apply rules to given points

The original point is $P(-1,2)$ and the new point is $P'(2,1)$.
If we consider a $-90^{\circ}$ rotation (clockwise rotation), for a point $(x,y)=(-1,2)$, the new point $(y,-x)$ is $(2,1)$.

Answer:

C. $-90^{\circ}$ rotation