Question

The image of a point is C'(2, 7). A 90° clockwise rotation was performed to get this image. What were the coordinates of the pre-image?

(-7, -2)
(7, -2)
(-2, -7)
(-7, 2)

Answer 1

Rotation 90° clockwise maps (x, y) → (y, −x). If the image is (2, 7), then y = 2 and −x = 7, so x = −7. The pre-image is (−7, 2).