It is the vertex. It can also be called the apex but that has a connotation of being the top-most point and so is not appropriate when both nappes are concerned.
It will be a hyperbola.
An Ellipse
hyperbola
ellipse
It is the vertex. It can also be called the apex but that has a connotation of being the top-most point and so is not appropriate when both nappes are concerned.
The intersection forms a hyperbola.
A hyperbola
edge-Apex
if a right circular cone intersects a plane that goes through both nappes of the cone, but not through the vertex, the resulting curve will be a hyperbola
Hyperbola
A hyperbola.
It will be a hyperbola.
A right circular cone looks like a martini glass. Actually, the martini glass is only a part of one half of the cone. Think also of an ice cream cone, again being part of one half. Formally, the right circular cone is the surface in three-dimensional space swept by a line that intersects a point and the domain of the circumference of a circle, said point lying on a line perpendicular (right angle) to the circle and intersecting its radius. Since the line sweeps through a point, there are two nappes, one on each side of that single point. The perpendicular line is called the axis, and the point is called the vertex.
An Ellipse
hyperbola
hyperbola