If AT=A−1A^T = A^{-1}AT=A−1, what can be said about the eigenvalues λ\lambdaλ of AAA?
∣λ∣=1|\lambda| = 1∣λ∣=1
λ=0\lambda = 0λ=0
λ=±1\lambda = \pm 1λ=±1
λ\lambdaλ is real