Question Number 160528 by amin96 last updated on 01/Dec/21
$$\left(\mathrm{2}\boldsymbol{\mathrm{cosh}}\left(\boldsymbol{\mathrm{x}}\right)\boldsymbol{\mathrm{cos}}\left(\boldsymbol{\mathrm{y}}\right)\right)\boldsymbol{\mathrm{dx}}+\left(\boldsymbol{\mathrm{sinh}}\left(\boldsymbol{\mathrm{x}}\right)\boldsymbol{\mathrm{sin}}\left(\boldsymbol{\mathrm{y}}\right)\right)\boldsymbol{\mathrm{dy}}=\mathrm{0} \\ $$