高校数学の質問スレ Part437

　x^3 + y^3 - 3axy = 0,
　r = 3a cosθ sinθ /{(cosθ+sinθ)(1−cosθ sinθ)},
　S = (1/2) ∫[0,π/2] rr dθ = (3/2)aa,
　X = { (2/3)r cosθ } = (1/3S) ∫[0,π/2] r^3 cosθ dθ
　Y = { (2/3)r sinθ } = (1/3S) ∫[0,π/2] r^3 sinθ dθ
より
　X = Y = 0.80613305077a