(1)∵∠2=∠B (known)
∴AB‖DE (same angle, two parallel straight lines)
(2)∫≈ 1 =∠D (known)
∴AC‖DF (internal dislocation angles are equal and two straight lines are parallel)
(3) ∵∠ 3+∠ f = 180 (known)
∴AC‖DF (internal angles on the same side are complementary and two straight lines are parallel)