Here the intersection can be calculated by two straight lines or the plumb line toe on a straight line. Should two straight lines be cut, four points must be given. All points are digitized with #P and are automatically integrated. The first both points define first Just and the third and fourth point second Just. If the straight lines cut themselves, the intersection is filed in the construction buffer.
If the fourth point is not given (but with #CON or Return uncompletedly), Just a plumb line is liked by the third point on. The plumb line toe is filed in the construction buffer. The intersection is also indicated in the display segment and lines are drawn to the intersection or plumb line toe. Also these auxiliary constructions are extinguished with the new drawing again.
Also about the suitable button in the construction menu available.