A graphical construction of phase trajectories forẍ+φ(ẋ)g(x)+ψ(ẋ)h(x)= 0

This communication provides a graphical technique for the construction of the equation
\ddot{x} + \phi (\dot{x})g(x) + \psi (\dot{x})h(x) = 0
. This technique can be carried out with, at most, two triangles and a compass and is suited to the construction of phase plane trajectories of nonlinear second-order differential equations.