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定积分计算 ∫2(上)1(下)x/根号x-1 dx

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定积分计算 ∫2(上)1(下)x/根号x-1 dx
令t = x - 1,dt = dx
当x = 1,t = 0
当x = 2,t = 1
原式= ∫(0→1) (t + 1)/√t dt
= ∫(0→1) (t/√t + 1/√t) dt
= ∫(0→1) (√t + 1/√t) dt
= [(2/3)t^(3/2) + 2√t] | (0→1)
= (2/3) + (2)
= 8/3
再问: 定积分计算 ∫2(上)1(下)根号x-1/x dx 再帮个忙吧
再答: 令t = √(x - 1),t² = x - 1,2t dt = dx 当x = 1,t = 0 当x = 2,t = 1 原式= ∫(0→1) t/(1 + t²) • 2t dt = 2∫(0→1) t²/(1 + t²) dt = 2∫(0→1) (t² + 1 - 1)/(1 + t²) dt = 2∫(0→1) [1 - 1/(1 + t²)] dt = 2[t - arctan(t)]| (0→1) = 2{[1 - arctan(1)] - [0 - arctan(0)] = 2[1 - π/4] = 2 - π/2