# Math Help - Prove the theorem.

1. ## Prove the theorem.

Let $U=\mathbb{R} \setminus \{(0,0)\}$ ; let
$\omega \dfrac{-y dx + x dy}{x^2 + y^2}$
be a $1-$ from in $U$. Then $d\omega =0$ ,but there is no $0-$ form $g$ on $U$ such that $dg = \omega$