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

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*.