For every lineand every pointlnot onP, there is a unique linel, that passes throughmand does not intersect (is parallel to)P.l

If a straight line intersecting two straight lines makes the interior angles on the same side less than two right angles, then the two lines (if extended indefinitely) will meet on that side on which are the angles less than two right angles.

Show that these two postulates are equivalent on the plane.