x² + y² = 2y => r = 2sinθ
y = x => θ = π/4
∫∫ (x² + y²) dσ
= ∫(0→π/4) dθ∫(0→2sinθ) r³ dr
= ∫(0→π/4) (1/4)(16sin⁴θ) dθ
= 4∫(0→π/4) [(1 - cos2θ)/2]² dθ
= ∫(0→π/4) (1 - 2cos2θ + cos²2θ) dθ
= ∫(0→π/4) (1 - 2cos2θ) dθ + (1/2)∫(0→π/4) (1 + cos4θ) dθ
= (π/4 - 1) + (1/2)(π/4)
= 3π/8 - 1
追问范围不是π/2到π/4吗
追答直线y = x表示的角度范围是0到π/4
追问以及与x轴围成的,呵呵谢了啊
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