西安毛子科技大学XIDIANUNIVERSITY于是 (o(6),8)-(auex,6) ]=an(8,8)=a;(6j,8,)=aji(6),(8)-[8,agx ) -ag(8),6n)= a,(6,6,) = aj由是对称变换，有（(8,),8,)=(8,0(8,)即i, j =1,2,......n.αij = αji,所以A为对称矩阵。§9.6 对称矩阵的标准形 于是 ( ) 1 ( ), , n i j ki k j k      a =   =      1 ( , ) n ki k j k a   = =  ( , ) ji j j = a   ji = a ( ) 1 , ( ) , n i j i kj k k      a =   =      1 ( , ) n kj i k k a   = =  ( , ) ij i i = a   ij = a , , 1,2, , ij ji 即  = = i j n 所以A为对称矩阵． 由  是对称变换，有 (      ( ), , ( ) i j i j ) = ( )