1. The problem statement, all variables and given/known data If U is a 2 x 2 unitary matrix with detU=1. Show that |TrU|≤2. Write down the explicit form ofU when TrU=±2 2. Relevant equations Not aware of any particular equations other than the definition of the determinant and trace. 3. The attempt at a solution I have attempted this problem in several different ways to no avail. I'm pretty sure that the explicit form of U when the trace is 2 is simply the 2 x 2 identity matrix. I do know that Tr(AB) ≠ Tr(A)Tr(B) and U*U = I but not sure where to go with this. Any help is greatly appreciated.