如题所述
FC2 PPV 880231 那个
2.用柱面坐标:积分区域为 r《2sinθ, 0《θ《π
∫∫(x^2+y^2)dxdy=∫(0,π)dθ∫(0,2sinθ)r^3dr
=4∫(0,π)(sinθ)^4dθ=8∫(0,π/2)(sinθ)^4dθ=8*(3/4)(1/2)(π/2)=3π/2