A:一名中学生的体重约为400N
B:课桌的高度约为80cm
C:珠穆朗玛峰峰顶的大气压约为1.01×105Pa
D:拿起两只鸡蛋所用的力大约是1N
如图,在△ABC中,点D在AB上,且CD=CB,点E为BD的中点,点F为AC的中点,连结EF交CD于点M,连接AM.若∠BAC=45°,AM=4,DM=3,则BC的长度为( )
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