Questioning the validity of a proof in Gelfand & Fomin – math.stackexchange.com
ca-hercor
I was reading Gelfand&Fomin Calculus of Variations book, in which I found this
Lemma 2 If $\alpha(x)$ is continuous in $[a, b]$, and if $$\int_a^b
\alpha(x) h'(x)\, dx = 0$$ for every function ...