help with geometry app

[parisse]

The 3rd parameter is used to choose one point if the intersection has more than 1 point, if this 3rd arg is a point, the intersection point is choosed nearest to the 3rd argument, if it is a list, the intersection point is choosed *outside* the list (this is useful if for example you intersect a line and a circle, you know one of the intersection and are interested in the 2nd intersection point).
I don't think you can skip it with the current interface, but it should indeed be possible to enhance the UI to skip it if the 2 objects to intersect are lines. Anyway, you can simply re-enter the last argument by pressing Enter if you intersect 2 lines, the argument will be ignored. And you can remove the 3rd arg from SYMB view later if you want to have a clean description of your construction (or directly enter single_inter(GA,GB) from SYMB view).