求陰影部份的面積

2011-10-09 12:18 am

回答 (1)

2011-10-09 1:03 am
✔ 最佳答案
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△AFE : △AEC = △BFE : △BEC = 4 : 8 = 1 : 2
故設 △AFE 面積 = x , 則 △AEC = 2x ,
於是 △AED = 2x - 6
又 △ABE : △ AED = △BEC : △DEC = 8 : 6 = 4 : 3 ,
即 (x + 4) : (2x - 6) = 4 : 3
4(2x - 6) = 3(x + 4)
5x = 36
x = 7.2
△AED = 2x - 6 = 2*7.2 - 6 = 8.4陰影面積 = 7.2 + 8.4 = 15.6 cm²


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