F2 數學急

F2 數學急

Ka Wai

2009-06-13 5:01 pm

如圖急

http://cg-love.com/s1/mhnk25l.jpg

更新1:

但係點解43個area唔係藍色部份? 如圖 http://cg-love.com/s1/gc3fkz0.JPG

更新2:

哦哦哦- - 我明啦我以為係小徑,草地果d 原來個corner有building- -

回答 (1)

用戶9112

2009-06-13 6:25 pm

✔ 最佳答案

http://img171.imageshack.us/img171/2236/dogxgf.jpg

(a) Let BP= k metre
Radius of the blue part = 5m
Area of the blue part is (丌5^2)/2 =12.5丌

Radius of the red part = 5 - BP = 5-k
Angle XBY = 180 - 60 = 120
Area of the red part = 丌(5-k)^2(120/360)

Total area = 12.5丌 + 丌(5-k)^2(120/360) which is 43
丌(5-k)^2(120/360) = 43 - 12.5丌
丌(5-k)^2(120/360) = 3.73
(5-k)^2 = 3.56
5-k = 1.89
k= 3.11m

BP = 3.11 m

(b) the distance the dog travelled = arc AX + arc XY

=2丌(5)/2 + 2丌(1.89)*(120/360)

=19.66m

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F2 數學 急

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