circle area
2012-07-28 3:36 am
圖片參考：http://imgcld.yimg.com/8/n/HA00437808/o/701207270073613873413150.jpg
please show the step clearly.
thanks~
回答 (1)
2012-07-28 3:56 am
✔ 最佳答案
Let O be the centre of the semicircle.then ∠AOC = π - π/6 - π/6 = 2π/3.The shaded part + △AOC = sector AOC
The shaded part + (1/2) OA OC sin∠AOC = (1/2)OA²∠AOC
The shaded part + (1/2)(12/2)(12/2) sin(2π/3) = (1/2)(12/2)²(2π/3)
The shaded part + 18 √3/2 = 12π
The shaded part = 12π - 9√3 = 22.11cm²
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120727000051KK00736