: f(α)=x,, i=1,2,...,n.. g(α) = fi(α)g(e))+ f2(α)g(c,)+...+ f,(α)g(en)= g(e)f(α)+ g(82)f2(α)+ ... + g(en)f,(α)Zg(e,)f: (a)..g = Zg(e,)f, = g(e)fi + g(c2)f2 +..+ g(8n)fni-1810.2对偶空间V§10.2 对偶空间 1 1 2 2 ( ) ( ) ( ) ( ) ( ) ( ) ( ) n n  = + + + g f g f g f g        1 1 2 2 ( ) ( ) ( ) ( ) ( ) ( ) n n = + + + g f g f g f       1 ( ) ( ) n i i i g f   =   =      1 1 2 2 1 ( ) ( ) ( ) ( ) n i i n n i g g f g f g f g f     =  = = + + +  ( ) , 1,2, , i i f x i n  = =