Question

The coordinates of the vertices of figure MNOP are M(10, 12), N(23, 16), O(12, 17), and P(11, 25). Figure MNOP was rotated around the origin to produce figure MꞌNꞌOꞌPꞌ with vertices Mꞌ(12, −10), Nꞌ(16, −23), Oꞌ(17, −12), and Pꞌ(25, −11).

What was the degree of rotation?

° clockwise

Answer 1

Changes in a coordinate
`(x,\ y)` can be observed with 90 degree rotations about the origin.

90 degrees CW =
`(y,\ -x)`
180 degrees CW =
`(-x,\ -y)`
270 degrees CW =
`(-y,\ x)`

Let's observe M(10, 12) and M'(12, -10).
Since they switched and the x value became negative, it must have been a 90 degree rotation.