Re: [積分] 二重積分

[zone806 (乘風飛翔)]

※ 引述《piperyim (Dreams come true)》之銘言：
  ∫∫xsin(xy)dA  R:〔0,π〕×〔1,2〕

  π 2
 =∫∫xsin(xy)dydx
  0  1

  π        |y=2
 =∫-cos(xy)|    dx
  0         |y=1

  π
 =∫(cosx-cos2x)dx
  0


 = 0

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