DEFINITON7。 Matrices 矩阵 A square matrix A is called symmetric ifA=A. Thus A=[ail is symmetric if ai=ai forall i and i with 1≤ i<n and1≤j≤nM a t r i c e s 矩 阵 DEFINITION 7. A square matrix A is called symmetric if A = At . Thus A = [aij] is symmetric if aij = aji for all i and j with 1≤i≤n and 1≤j≤n