原式=∫dθ∫(1+rcosθ)²rdr (做变换:x=1+rcosθ,y=rsinθ.则dxdy=rdθdr)
=∫dθ∫(r+2r²cosθ+r³cosθ)dr
=∫[1/2+(2/3)cosθ+(1/4)cos²θ]dθ
=∫[5/8+(2/3)cosθ+(1/8)cos(2θ)]dθ
=[(5/8)θ+(2/3)sinθ+(1/16)sin(2θ)]│
=(5/8)(2π)
=5π/4.
原式=∫dθ∫(1+rcosθ)²rdr (做变换:x=1+rcosθ,y=rsinθ.则dxdy=rdθdr)
=∫dθ∫(r+2r²cosθ+r³cosθ)dr
=∫[1/2+(2/3)cosθ+(1/4)cos²θ]dθ
=∫[5/8+(2/3)cosθ+(1/8)cos(2θ)]dθ
=[(5/8)θ+(2/3)sinθ+(1/16)sin(2θ)]│
=(5/8)(2π)
=5π/4.