从D点作BC的垂线,垂足为F.
设BM=x,则DF=x,DE=MN=2,BC=6,AB=9,
AN=9-2-x=7-x,∠EAB=30°,EN=AN·tan30°=√3(7-x)/3,BF=EN,DF=CF=BC-BF
即x=6-√3(7-x)/3,解得x即为BM长.
从D点作BC的垂线,垂足为F.
设BM=x,则DF=x,DE=MN=2,BC=6,AB=9,
AN=9-2-x=7-x,∠EAB=30°,EN=AN·tan30°=√3(7-x)/3,BF=EN,DF=CF=BC-BF
即x=6-√3(7-x)/3,解得x即为BM长.