## Parallel Lines Property Theorem

Theorem 1 Two lines perpendicular to the same line are parallel. Theorem 2 Parallel lines are equidistant everywhere. Theorem 3 Two parallel straight lines are intercepted by a third straight line, and the interior angles are equal. Proof: Theorem 1 straight linel2⊥l3l2⊥l3, to prove:l1l1andl3l3hand over separatelyl2l2AtBB, you can passl1l1parallel linesPP，l2l2，BB, ( the property theorem that parallel lines are perpendicular to …