Answer:
B. 180° about the origin
Step-by-step explanation:
You are given a figure and its image, and asked to determine the angle of rotation. All of the answer choices indicate the center of rotation is the origin.
__
You have two clues that the rotation is 180° about the origin:
- The original figure is in the 2nd quadrant, and the image is in the 4th quadrant, directly opposite the origin.
- Line ST is directed to the northeast; line S'T' is directed to the southwest, in exactly the opposite direction.
__
To find the angle of rotation, you can look at the angle formed by a point, the center of rotation, and the image of the original point. Here, the angle UOU' is a straight angle, so the angle of rotation about O is 180°--the measure of that angle. (It can be convenient to use points close to the center of rotation, but any corresponding points on preimage and image will do.)
