如图,已知∠1 =∠2,∠B =∠C,可推得AB∥CD。理由如下: ∵∠1 =∠2(已知) 且∠1 =∠CGD(__________________________) ∴∠2 =∠CGD(等量代换) ∴CE∥BF(_______________________________) ∴∠_____=∠BFD(__________________________) 又∵∠B =∠C(已知) ∴∠BFD =∠B(等量代换) ∴AB∥CD(________________________________) |