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设区域D={(x,y)|x²+y²≤1,x≥0},计算二重积分I=∫∫(1+xy)/(1+x²+y²)dxdy
人气:336 ℃ 时间:2019-09-27 18:43:07
解答
原式=∫(-π/2,π/2)dθ∫(0,1)[(1+r²sinθcosθ)/(1+r²)]rdr (极坐标变换)=1/2∫(-π/2,π/2)dθ∫(0,1)[(1+rsinθcosθ)/(1+r)]dr (用r代换r²)=1/2∫(-π/2,π/2)dθ∫(0,1){1/(1+r)+[1-1/(1+r)]si...
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