Parabolic cylinder
= Parabolic cylinder
{title2=$x=c-y^2/(4c),\quad c>0$}
A <quadric surface> obtained by extending a <parabola> along a fixed direction outside its plane. For example, $x=c-y^2/(4c)$ with arbitrary $z$ is a parabolic cylinder parallel to the $z$ axis. Each cross-section of fixed $z$ has vertex $(c,0)$ and focus $(0,0)$ in its $xy$ plane. It occurs as a coordinate surface in <parabolic cylindrical coordinates>.