ω² as a function of s₀/L (Eq. (41)) for the three solutions obtained in Fig. 6. The solid lines correspond to (lines decreasing from left to right) and (lines increasing from left to right), and the dashed lines to . The horizontal line represents ω = 0 and divides the plot into stable and unstable solutions. In this plot the left and right solutions are stable while the near apex solution is unstable. The bifurcation points (vertical dashed lines) have been calculated by solving Eqs. (23) and (24) simultaneously, and it is equivalent to impose ω² = 0 in Eq. (41) once s_e is known.