Show that if $\omega$ is a 1-form differential define on $U\subset\mathbb{R}^{n}$, $c:[a,b]\to U$ is a differentiable curve and $\vert\omega(c(t))\vert\leq M$, for all $t\in [a,b]$, then $$\left\vert\int_{C}\omega\right\vert\leq ML$$ where L is a lenght of c.
I think with Poincare's lemma is useful for this, but I don't know why.. regards!