Draws a conic section curve.
Steps:
Pick the start.
Pick the end.
Pick the apex.
This location partially defines the plane for the conic.
Pick a location for the conic to pass through to define its curvature.
 or 
Type a the rho value (a number greater than 0 and less than 1), and press Enter.
Options
Pick the apex ("top" control point).
Drag the perpendicular indicator to the desired location on an existing curve.
Drag the tangent indicator to the desired location on an existing curve.
Types of conics
Ellipse A closed planar section curve of a right circular cone. Rho values greater than 0.0 and less than 0.5. 

Parabola The intersection of a right circular cone and a plane that passes through the side of the cone and the base of the cone. Rho value of 0.5. 

Hyperbola The intersection of a right circular cone and a plane perpendicular to the cone's base. Rho values greater than 0.5 and less than 1. 
Note: The status bar displays the rho value during the command.
Curve > Conic Curve > Conic 
Draws a closed elliptical curve.
Steps:
Follow the prompts for the selected option. If no option is specified, the default is used.
Options
Creates the ellipse from the center, first axis, and second axis.
Pick the center.
Pick the end of the first axis.
Pick the end of second axis.
Draws the ellipse center point and axes perpendicular to the construction plane.
Pick the center.
Pick end of the first axis.
Pick the end of the second axis.
Draws an ellipse from the corners of an enclosing rectangle.
Pick a corner for the enclosing rectangle.
Pick the opposite corner of the enclosing rectangle.
Draws an ellipse from points on its axes.
Pick the start of the first axis.
Pick the end of the first axis.
Pick the end of the second axis.
Draws an ellipse from focus points and a point on the curve.
Pick the first focus.
Pick the second focus.
Pick a point on the ellipse curve.
Option
MarkFoci
Places a point object at the focus locations.
Draws an ellipse around a curve.
Pick the center on a curve.
Pick the end of the first axis.
Pick the end of the second axis.
Ellipse > Ellipse: From Center Main2 > Ellipse: From Center Curve > Ellipse > From Center 
Draws a hyperbolic curve from coefficient values, foci, or vertices.
Steps:
Follow the prompts for the selected option. If no option is specified, the default is used.
Options
Draws the hyperbola from the center, focus, and end.
Pick the center.
Pick the focus.
Pick the end.
Uses the A and B coefficients of the hyperbola equation to define the curve.
Pick the center.
Pick a direction.
Pick the end.
Options
A/B
The coefficients of the equation that defines the hyperbola. The A coefficient represents the distance from the center point to the vertex of the hyperbola. If C is the distance from the center point to the foci of the hyperbola, then B2 = C2  A2. The B coefficient can be considered the slope of the asymptotes.
Draws the hyperbola starting from the focus points.
Pick the first focus.
Pick the second focus.
Pick the end.
Places a point object at the focus locations.
Draws the hyperbola starting from the vertices.
Pick the vertex.
Pick the focus.
Pick the end.
Draws both branches of the hyperbola.
Displays the asymptotes of the hyperbola as it is drawn.
Curve > Hyperbola Curve > Hyperbola > Center, Focus 
Draws a parabolic curve from the focus or vertex locations.
Steps:
Follow the prompts for the selected option. If no option is specified, the default is used.
Options
Places a point object at the focus location.
Draws only half the parabola.
Draw a parabolic curve from focus point, direction, and end.
Pick the focus.
Pick a direction.
This is the "open" direction.
Pick the end.
The focus to vertex distance and length of the parabola display at the command prompt.
Draw a parabolic curve from vertex point and end.
Pick the vertex.
Pick the focus.
This is the "open" direction.
Pick the end.
The focus to vertex distance and length of the parabola display at the command prompt.
Curve > Parabola by Focus Curve > Parabola > Focus, Direction 