Question

Given: m<4 + m<7 = 180 degrees
Prove: c || d

Answer 1

1) m∠4 + m∠7 = 180° (given)

2) ∠4 is congruent to ∠6 (vertical angles)

3) m∠4 = m∠6 (definition of congruent angles)

4) m∠6 + m∠7 = 180° (substitution)

5) c is parallel to d (converse of same side interior angles theorem)