Intersection of a planes normal to each curve. Works with intersecting curves as well as straight lines.
Plane with AroundCurve option. Pick one curve and use intersection of the curves as the point on the curve. Drag corner of plane to make it sufficiently large. Repeat for the other curve.
Intersect the planes.
Trim / extend the line as needed.
A command which accepts two intersecting
curves as input and outputs a normal line would be helpful.
