注意 11 12 22 12 A22 AA 2 n2 nn In 2n nn A 0 0 041 =AE同理AA=AE 00 (1)A4=A*A=AE(d) c a注意： * AA                         = n n nn n n n n nn n n A A A A A A A A A a a a a a a a a a               1 2 1 2 2 2 2 1 1 2 1 1 1 2 2 1 2 2 2 1 1 1 2 1             = A A A        0 0 0 0 0 0 = AE A A = AE 同理 * AA = A A = AE * * (1)       − − =       c a d b c d a b * (2)