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標題:

計圓周一題.....10分

發問:

The figre is formed by sectors OAB and OCD . C and D are point on OA and OB respectively.If OB =4cm,OD=1／2 OB and ∠COD = 150°,find the perimeter of the figue

最佳解答:

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哈!我今日放學岩岩要做BCA,裡面有條一樣既= = aaa.....(圓周率=3.14...) 圓周=2*圓周率*4*210/360+2*圓周率*2*150/360 =(14*圓周率)/3+(5*圓周率)/3 =(19*圓周率)/3 =19.8967534727 =20cm(我記得好似係取至整數既)

其他解答:

C and D are point on OA and OB respectively, so OCA and ODB are straight lines, such that sector OCD overlaps sector OAB. ∴∠COD = ∠AOB = 150° The perimeter of the figue = 2OB * π * 150°/360° = 2*4 * π * 150°/360° = 10.5 cm^2 (corr. to 3 sig. fig.) The information of OD=1／2 OB is useless here. 2008-03-14 20:33:27 補充： My answer should add 2OB, and not cm^2 as the unit, sorry. i.e., 10.5+8 = 18.5cm|||||arc AB=2*3.14*4*15/360 cm =1.04667 cm perimeter=1.04667+4*2 cm =9.05 cm(cor. to 3 sig. fig.)|||||請問有無圖呢?? 無圖係幫唔到你嫁 有圖先可以做嫁9B623C59CC17F40C