- 
                            If a point is selected (mono-tangent mode): a vector tangent to the
                                curve is displayed at the selected point. 
- 
                            If a second curve is selected (or a point in bi-tangent mode), you
                                need to select a support plane. The line will be tangent to both
                                curves. 
                        Line tangent to curve at a given point

                            
                        
                    
                    When several solutions are possible, you can choose one
                        (here displayed in green) directly in the geometry, or using Next
                            Solution
                         :
:
                    Line tangent to two curves
