设EH长为x,则HC=EC-EH=10-x
FH/BC=EH/EC
FH=BC*EH/EC=8*x/10=4x/5
阴影面积 = 1/2*(AF+HD)*HC=1/2(AD-FH)*HC=1/2(BC-FH)*HC=1/2(8-4x/5)*(10-x)
三角形EFH面积 = 1/2*FH*EH = 1/2*4x/5*x
1/2(8-4x/5)*(10-x) - 1/2*4x/5*x = 8
(10-x)² - x² = 20
100-20x = 20
x = 4
答:EH长4厘米.
设EH长为x,则HC=EC-EH=10-x
FH/BC=EH/EC
FH=BC*EH/EC=8*x/10=4x/5
阴影面积 = 1/2*(AF+HD)*HC=1/2(AD-FH)*HC=1/2(BC-FH)*HC=1/2(8-4x/5)*(10-x)
三角形EFH面积 = 1/2*FH*EH = 1/2*4x/5*x
1/2(8-4x/5)*(10-x) - 1/2*4x/5*x = 8
(10-x)² - x² = 20
100-20x = 20
x = 4
答:EH长4厘米.