Tricritical wing critical edge
= Tricritical wing critical edge
{title2=$M_c^2=-3u/(10v)$}
= Wing critical edge
{synonym}
For $f=rM^2/2+uM^4/4+vM^6/6-hM$ with $v>0$, the ordinary critical edge of a <tricritical wing> satisfies $f^{(1)}=f^{(2)}=f^{(3)}=0$. For $u<0$, $M_c^2=-3u/(10v)$, $r_c=9u^2/(20v)$ and $h_c=6u^2M_c/(25v)$. Its fourth derivative is $-12u>0$. The two signs of $M_c$ give the two wings.