5.3.1特殊矩阵 11 13 21 a 2 a 2a23 Anxn a31a32a33 an n1 n n 3 nn 对称矩阵:a1;=a1(1<=i,j-n) 下三角矩阵:当i<j时,aij=0,(1<=i,j=n 三对角矩阵:当|1-j>1时,a1;=0,(1<=i,j=n5.3.1 特殊矩阵 对称矩阵: aij = aji (1<=i,j<=n) 下三角矩阵: 当i<j时, aij = 0, (1<=i,j<=n) 三对角矩阵: 当|i-j| > 1时, aij = 0, (1<=i,j<=n) a11 a12 a13 ... a1n a21 a22 a23 ... a2n a31 a32 a33 ... a3n ...... an1 an2 an3 ... ann Anxn =