now look at the converse of the proceeding theoreman proof who we begin with the given that two lines of parallel instead of the given of the sum of the interior angles formed is 180° in the next diagram LM while AB and BC a transversials
ABC Must be 180 degrees because we have formed a Triangle. Using the Triangle Angle Sum therom all angles within the triangle must add up to a 180 degrees hence 180s is needed for the triangle
