If AAA has eigenvalues λ1,λ2\lambda_1, \lambda_2λ1,λ2, what are the eigenvalues of ATA^TAT?
λ1,λ2\lambda_1, \lambda_2λ1,λ2
1/λ1,1/λ21/\lambda_1, 1/\lambda_21/λ1,1/λ2
−λ1,−λ2-\lambda_1, -\lambda_2−λ1,−λ2
λ12,λ22\lambda_1^2, \lambda_2^2λ12,λ22