Click the Curve ► Conic command 
in the Geometry
menu. The dialog box for the command appears.
Type a Tolerance value into the box, if required. The smaller the tolerance value, the smoother the curve appears on the screen. As the curve is mathematically defined, changing this modifier does not alter the actual shape of the curve.
Type a Name for the curve, if required.
Click on OK to accept the parameters and dismiss the dialog box.
Digitise in response to the ‘Digitise first tangent’ prompt. Either, make an entity digitise on a line entity (d1) or digitise two positions that define a tangent line.
Digitise in response to the ‘Digitise second tangent’ prompt. Either, make an entity digitise on a line entity (d2) or digitise two positions that define a tangent line.
Digitise a position in response to the ‘Digitise shoulder point’ prompt (d3). The control points can be full 3D points.
