直线I与BC交于M点,DN垂直于直线I于N,
h1/h2=DM/(BD+DM), h1/h3=DM/(BD-DM),
所以h2=[(BD+DM)/DM]*h1,h3=[(BD-DM)/DM]*h1,
所以h2-h3={[(BD+DM)/DM]-[(BD-DM)/DM]}*h1=2h1
/是除以,*是乘以
直线I与BC交于M点,DN垂直于直线I于N,
h1/h2=DM/(BD+DM), h1/h3=DM/(BD-DM),
所以h2=[(BD+DM)/DM]*h1,h3=[(BD-DM)/DM]*h1,
所以h2-h3={[(BD+DM)/DM]-[(BD-DM)/DM]}*h1=2h1
/是除以,*是乘以