If A2 = A for an invertible n n matrix A, then A must be
Chapter 2, Problem 40(choose chapter or problem)
If A2 = A for an invertible n n matrix A, then A must be In.
Unfortunately, we don't have that question answered yet. But you can get it answered in just 5 hours by Logging in or Becoming a subscriber.
Becoming a subscriber
Or look for another answer