(a) Plot A'B'C', the image of ABC after a clockwise rotation of 90 degrees about point D. Give the coordinates of the vertices below. (b) A'B'C has the same size and shape as ABC. Why is this true?

Question

Geometry: Transformations, Rigid Motions, and Congruence.

Answer 1

For section A, the rule for a 90 degree rotation clockwise is change your original point (x, y) to the rotated point (y, -x). So for example, if a point (1, 2) was rotated 90 degree clockwise, then the rotated point would be (2, -1).

For section B, think about rotating an everyday object, like your phone. Simply rotating the phone will not change its size and shape because rotation is not a type of transformation that results in a change in size and shape. Dilation would change the size, for example.