A = ∫∫V·n dS
= ∫∫xzdydz + yx²dzdx + zy²dxdy
∑的法矢量与x轴夹角始终不大于π/2
则∫∫xzdydz = ∫∫z√(1-y²)dydz = ∫(0,1)dy∫(0,1)z√(1-y²)dz = π/8
y>0时,∑的法矢量与y轴成锐角
y
A = ∫∫V·n dS
= ∫∫xzdydz + yx²dzdx + zy²dxdy
∑的法矢量与x轴夹角始终不大于π/2
则∫∫xzdydz = ∫∫z√(1-y²)dydz = ∫(0,1)dy∫(0,1)z√(1-y²)dz = π/8
y>0时,∑的法矢量与y轴成锐角
y