由题意得:
AB/BE=1/2,DF/FE=1/2,即影长是物长的2倍.
因为角DCF=30度,所以DF=CD/2=2m,则FE=2DF=4m
CF^2=CD^2-DF^2
则CF=2√3m
所以:BE=BC+CF+FE=10m+2√3m+4m=14+2√3m
AB=BE/2=7+√3m≈8.732m
由题意得:
AB/BE=1/2,DF/FE=1/2,即影长是物长的2倍.
因为角DCF=30度,所以DF=CD/2=2m,则FE=2DF=4m
CF^2=CD^2-DF^2
则CF=2√3m
所以:BE=BC+CF+FE=10m+2√3m+4m=14+2√3m
AB=BE/2=7+√3m≈8.732m