The diagram shows two parallel lines crossed by a transversal. All pairs of angles in such a situation are either CONGRUENT (they have the same measure) or SUPPLEMENTARY (they add up to 180°). To practice your identification skills: 1. Press the Random button to create a new diagram. 2. Decide if the two angles are congruent or supplementary to each other. 3. Click on "Show answer:" to check your answer.