Question

The rule (x,y) ---> (-x,-y)
results in which of the following rigid motions?
A.
reflection across the y-axis

B.
reflection across the line y = x

C.
90° clockwise rotation about the origin

D.
180° counterclockwise rotation about the origin

Answer 1

D. 180° counterclockwise rotation about the origin.

Reason: rotating (x,y) by 180° about the origin sends it to (-x,-y). (Reflection across the origin is the same as a 180° rotation.)