计算x2dydx+y2dzdx+z2dxdy,其中∑:(x-1)2+(y-1)2+z2/4=1(y≥1),取外侧.

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问题 计算x2dydx+y2dzdx+z2dxdy,其中∑:(x-1)2+(y-1)2+z2/4=1(y≥1),取外侧.

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答案令∑0:y=1(Dxz:(x-1)2+z2/4≤1),取左侧, 则原式=[*]x2dydz+y2dzdx+z2dxdy-[*]x2dydz+y2dzdx+z2dxdy=I1-I2, I1=[*]x2dydz+y2dzdx+z2dxdy=2[*][(x+y+z)dv=2[*](x+y)dv 令[*](0≤θ≤π,0≤φ≤π,0≤r≤1),dv=2r3sinφdrdθdφ,则 I1=4∫0πdθ∫0π(cosθsin2φ/4+sinθsin2φ/4+2sinφ/3)dφ =4∫0π(πcosθ/8+πsinθ/8+4/3)dθ=19π/3, I2=[*]x2dydz+y2dxdy+z2dxdy=[*]y2dzdx=-[*]dzdx=-2π, 故原式=19π/3+2π=25π/3.

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