Question

Jack discovers that the orientation of a triangle is counterclockwise. He then reflects the triangle over the y-axis. What is the orientation of the reflected figure?
A. There is not enough information to tell.
B. The reflected figure has a counterclockwise orientation.
C. The orientation could be clockwise or counterclockwise depending on how you do the reflection.
D. The reflected figure has a clockwise orientation.

Answer 1

D. Reflection across the y-axis reverses orientation (it’s an orientation-reversing isometry). For example, triangle (0,0) → (1,0) → (0,1) is counterclockwise; reflecting across the y-axis gives (0,0) → (−1,0) → (0,1), which is clockwise.