已知,CM是Rt△ABC斜边上的中线,（题中应该是∠A小于∠B）可得：CM = AM ,所以,∠ACM = ∠BAC .∠BCD = 90°-∠B = ∠BAC = ∠ ACM = ∠DCM .因为,∠BCD + ∠ ACM + ∠DCM = 90° ,即有：3∠BAC = 90° ,所以,∠BAC =...