Let V be a finite-dimensional vector space and f a non-degenerate symmetric bilinear form on V. Show that for each linear operator T on V there is a unique linear operator T′ on V such that f(Tα,β)=f(α,T′β) for all α, β in V. Also show that
(T1T2)′=T2′T1′(c1T1+c2T2)′=c1T1′+c2T2′(T′)′=T.
How much of the above is valid without the assumption that T is non-degenerate?