Solution (source code)

= Solution

Writing the <differential one-form> as $M\,dx+N\,dy$, its coefficients satisfy $M_y=e^y\cos x=N_x$. It is an <exact differential form>, with potential $F=(1+e^y)\sin x$, because
$$
dF=(1+e^y)\cos x\,dx+e^y\sin x\,dy.
$$
The implicit solution is therefore
$$
\boxed{(1+e^y)\sin x=C.}
$$