Rewrite dydx=f(x)g(y)\frac{dy}{dx} = f(x)g(y)dxdy=f(x)g(y) as ∫dyg(y)=∫f(x) dx\int \frac{dy}{g(y)} = \int f(x) \, dx∫g(y)dy=∫f(x)dx.
