Question

What is a valid reason for stating that: http://curriculum.kcdistancelearning.com/courses/GEOMx-HS-A09/a/assessments/IP-IntroductionProofUnitExam/Geometry_Unit2_Exam_89q1.gif

here:http://curriculum.kcdistancelearning.com/courses/GEOMx-HS-A09/a/assessments/IP-IntroductionProofUnitExam/Geometry_Unit2_Exam_89q2.gif

Answer 1

well those angles are called alternate angles and their is a theorem saying that if the lines are parallel then the angles are equal ..

Answer 2

if you want a proof of this see -- http://www.proofwiki.org/wiki/Parallel_Implies_Equal_Alternate_Interior_Angles,_Corresponding_Angles,_and_Supplementary_Interior_Angles