  This paper presents a method for the analysis of process $J/\psi \rightarrow
\rho\pi \rightarrow \pi^+\pi^-\pi^0$ based on the consideration of the angles
of expansion of finite pion pairs. The proposed approach makes it possible to
effectively carry out selection of events in both neutral and charge-conjugate
modes of the decay of $J/\psi \rightarrow \rho\pi$. Application of the method
for the analysis of similar three-body decays in some cases will simplify the
analysis and refine current results.
