又 (α)=x,o(s,),(β)=Zy,o(8)i-1由于α(),α(,),,(c,)为标准正交基，得(o(α),0(β)=Zx,y;:. (o(α),o(β))=(α,β)故是正交变换。$9.4正交变换§9.4 正交变换 ( ) 1 ( ), ( ) n i i i     x y = =  故  是正交变换． 1 ( ) ( ) n j j j     y = ( ) ( ), 1 =  n i i i     x = 又 =   = (      ( ), ( ) ( , ) ) 由于       ( ), ( ), , ( ) 1 2 n 为标准正交基，得