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不定积分x^2dx/(a^2-x^2)^(1/2) (a>0)

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不定积分x^2dx/(a^2-x^2)^(1/2) (a>0)
不定积分x^2dx/(a^2-x^2)^(1/2) (a>0)
令x = a siny,dx = a cosy dy
∫ x²/√(a² - x²) dx
= ∫ (a² sin²y)(a cosy dy)/(a cosy)
= a²∫ sin²y dy
= (a²/2)∫ (1 - cos2y) dy
= (a²/2)(y - 1/2 sin2y) + C
= (a²/2)arcsin(x/a) - (a²/2)siny cosy + C
= (a²/2)arcsin(x/a) - (a²/2)(x/a) √(a² - x²)/a + C
= (a²/2)arcsin(x/a) - (x/2)√(a² - x²) + C