ACTIVITY 1 Prove that if two parallel lines are cut by a transversal, then the alternate interior angles are congruent. Discuss and show the proof. Given: а || b with transversal t cutting a and b. Prove: 2226 Reason 1.. Figure: Proof: Statement m_2 + m27 = 180 m_7 + m26 = 180 m_2 + m27 = m_7 + m26 m_7 = m_7 2. Transitive Prop. 3. 4. Subtraction Prop. .22 =26 5. Def. of congruent angles.