∫(1,0) x^2/sqrt(1-x^2) dx设 sinθ = x∫(1,0) x^2/sqrt(1-x^2) dx = ∫(π/2, 0) sinθ^2/cosθ d(sinθ)= ∫(π/2, 0) sinθ^2/cosθ cosθdθ= ∫(π/2, 0) sinθ^2 dθ= ∫(π/2, 0) (1/2 - cos2θ/2) dθ= (0-π/4) - sin2θ /4 | (π/2, 0)= -π/4 + 0 = -π/4