如图,在Rt△ABC中,∠C=90°,M为AB的中点,AC∥MN,AM=AN,求证：MN=AC

延长BA到Q,使AQ= AM, 联结NQ因为 AM = AN, 所以∠ANM = ∠AMN因为 AQ = AN, 所以∠AQN = ∠ANQ∠ANM + ∠AMN + ∠AQN + ∠ANQ = 180°所以∠ANM+ ∠ANQ = 90°AC// MN所以∠CAB = ∠NMQ∠B = 90° - ∠CAB∠Q = 90°...