Exercise 3. Are the followig matrices symmetric, skew-symmetric or orthog- onal? Calculate their eigenvalues and state what you would expect about tthe eigenvalues from the theorems discussed in the lecture. 6 0 0 0 9 -12 A = = (-0086 0.8); B = 0 2 -2 ; C = -9 0 20 0-2 5 12 -20 0