Re: [積分] 二重積分
※ 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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