Question

Triangle UVW is drawn with vertices at U(−1, 1), V(0, −4), W(−4, −1). Determine the coordinates of the vertices for the image, triangle U′V′W′, if the preimage is rotated 90° counterclockwise.

U′(1, −1), V′(0, 4), W′(4, 1)
U′(−1, −1), V′(4, 0), W′(1, −4)
U′(−1, 1), V′(4, 0), W′(1, 4)
U′(−1, 1), V′(0, −4), W′(−4, −1)

Answer 1

The correct answer is U′(1, −1), V′(4, 0), W′(1, 4). When a point is rotated 90° counterclockwise about the origin, the x-coordinate and y-coordinate change places, and the sign of the new x-coordinate is the opposite of the original y-coordinate. So for example, point U(−1, 1) becomes U′(1, −1).