→ shingai : 我好像了解你的意思..不過他沒納進矩形邊界 (對吧?!04/28 13:40
想了另外一個解法
cos(2x) = cos(y)
-1
y = cos ( cos (2x) )
y 對 x 作圖 , 圖形週期為 π => Area (x=0..π) = Area (x =π .. 2π)
且 cos( 2 (π/2 + x ) ) = cos( 2( π/2 - x ) )
y 在 0..π 對稱於 x = π/2
x=0..π/2 => y = 2x
x= 0 => y = 0
x= π/2 => y = π
答案就是四個三角形相加
=> 4 * [ (1/2) * π/2 * π ] = π^2
有錯還請不吝指正。
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If people do not believe that mathematics is simple,
it is only because they do not realize how complicated life is.
－ John von Neumann
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※ 編輯: a016258 (140.114.137.240), 04/28/2015 15:51:01