特别当A是n阶方阵时AE=EA 2.对角阵 40 0 0 az 0 diag(a,a2,,a)= 0 0 an)nxn diag(a,az,,a)tdiag(b,b2,..,b) =diag(a1±b,a2±b2,,an±bn) 上页 这回特别当 A 是 n 阶方阵时 A E = E A 2. 对角阵 ( ) n n n n a a a diag a a a                =         0 0 0 0 0 0 , , , 2 1 1 2 * ( ) ( ) ( ) n n n n diag a b a b a b diag a a a diag b b b =     , , , , , , , , , 1 1 2 2 1 2 1 2   