I have to prove the following:

Prove euclidean parallel postulate iff parallel lines are equidistant from one another. My hint is this:

Use the converse to Theorem 4.1 since it can be proved assuming Neutral geometery + euclidean parallel postulate. " Parallel lines are equidistan from one another" if the length of all perpendicular segments from a point on line "dropped" to the other line are congurent[equal in length].