[Extend Curve] command extends(extrapolates) an existing curve smoothly. Smooth means that the extrapolated part will have C2 continuity, that is, their tangents and curvatures are continuous.
For the prompt
"Specify around an end point of a curve"
, mouse-click around the end
point of a curve to extend. On mouse-clicking the input dialogue appears.
After inputing various parameter values, press OK button.
Input the chord length for the extending part of the curve.
Specify how the extrapolating part should change by the value between 0.0 and 1.0.
Pressing this button updates the screen preview of teh extending curve.