What is the trace of a 2×22 \times 22×2 matrix AAA with eigenvalues λ1\lambda_1λ1 and λ2\lambda_2λ2?
λ1λ2\lambda_1 \lambda_2λ1λ2
λ1+λ2\lambda_1 + \lambda_2λ1+λ2
λ1−λ2\lambda_1 - \lambda_2λ1−λ2
λ1λ2\frac{\lambda_1}{\lambda_2}λ2λ1