I am trying to find out whether the following equation is exact or not:
\begin{equation} (2k \sin(k + l) + \cos(k + l))dk + \cos(k + l)dl = 0 \end{equation}
I learned from my math book that you can check if the equation is exact by finding if $\Psi_{kl}$ = $\Psi_{lk}$
so going back to my equation I have:
\begin{equation} (2k \sin(k + l) + \cos(k + l)) \neq \cos(k + l) \end{equation}
since the two terms are not equal the differential equation is not exact right?
Also how would I solve this differential equation? I have no idea how to do it.
Moreover, I know that the variables k and l are related and l is dependent and k independent and also that it has an integrating factor g(k).