Elliptic lines in the Klein model.

This simple sketch let's you construct lines between two given points in the Klein model for elliptic geometry. In this model, the circle represents the whole plane, lines are diameters of the circle or arcs of circles that intersect the given circle on a diameter's endpoints.

Plot two points inside the circle. To construct the elliptic line, click on the custom tool on the toolbar. Then select the circle and the two points.