积分 ∫x^3/(1-x^2)^(3/2)dx
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积分 ∫x^3/(1-x^2)^(3/2)dx
![积分 ∫x^3/(1-x^2)^(3/2)dx](/uploads/image/z/8274763-19-3.jpg?t=%E7%A7%AF%E5%88%86+%E2%88%ABx%5E3%2F%281-x%5E2%29%5E%EF%BC%883%2F2%EF%BC%89dx)
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答:
∫[x³/(1-x²)^(3/2)]dx
=∫[x³/(1-x²)√(1-x²)]dx 设x=sint,-π/2<t<π/2
=∫(sin³t/cos³t)d(sint)
=∫(sin³t/cos²t)dt
=-∫(sin²t/cos²t)d(cost)
=∫[(cos²t-1)/cos²t]d(cost)
=cost+1/cost+C
=√(1-x²)+1/√(1-x²)+C
=(2-x²)/√(1-x²)+C
再问: x=sint 那么x就把限制在了1到-1 x应该不等于正负1就行了啊
再答: x³/(1-x²)^(3/2)本来就限定了-1