∫[0,1]dx∫[0,√x-x^2](x^2+y^2)^-1/2 dy
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本题主要求y=x²的极坐标方程,即rsinθ=r²cos²θ,整理后为:r=sinθ/cos²θ
则∫(0->1)dx∫(x^2->x)(x^2+y^2)^(-1/2)dy
=∫[0->π/4]dθ∫[0->sinθ/cos²θ] (1/r)*rdr
=∫[0->π/4]dθ∫[0->sinθ/cos²θ] 1dr
=∫[0->π/4] sinθ/cos²θdθ
=-∫[0->π/4] 1/cos²θd(cosθ)
=1/cosθ [0->π/4]
=√2-1
则∫(0->1)dx∫(x^2->x)(x^2+y^2)^(-1/2)dy
=∫[0->π/4]dθ∫[0->sinθ/cos²θ] (1/r)*rdr
=∫[0->π/4]dθ∫[0->sinθ/cos²θ] 1dr
=∫[0->π/4] sinθ/cos²θdθ
=-∫[0->π/4] 1/cos²θd(cosθ)
=1/cosθ [0->π/4]
=√2-1
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不要复制ok?答案也不对
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