### Home > PC > Chapter 12 > Lesson 12.2.2 > Problem12-51

12-51.

Earlier we found the matrix associated with the composition of rotating 90° counterclockwise and then reflecting across the x-axis. Now find the matrix associated with reflecting across the x-axis and then rotating 90°. Homework Help ✎

From problem 12-45:
A = matrix associated with 90º counterclockwise rotation
B = martix associated with reflecting across the x-axis

Multiply A and B in the opposite order you did in problem 12-45. That is, find BA.