Let $\omega\_t$ be an exact form depending smoothly on time $t$. 

Then is $\dfrac{d\omega\_t}{dt}$ also exact?

$\dfrac{\omega\_t - \omega\_{t\_0}}{t-t\_0}$ is clearly exact. 

However I am stuck in showing that its limit is exact. 

Thanks in advance. 

**Using Ted's hint**

Let $c$ be an any smooth k-cycle. Since $\omega\_t$ is exact, $\displaystyle\int\_c \omega\_t =0$ 

It suffices to prove that $\displaystyle\int\_c \lim\_{t \to t\_0} \dfrac{\omega\_t - \omega\_{t\_0}}{t-t\_0} = \lim\_{t \to t\_0}\displaystyle\int\_c \dfrac{\omega\_t - \omega\_{t\_0}}{t-t\_0} $.

However this is on the world of manifolds and diffenretial forms, I am not sure it works well.