求x.e^x/(e^x-1)^1/2的积分
1个回答

∫x.e^x/ √(e^x-1) dx

= 2∫ xd√(e^x-1)

= 2x√(e^x-1) - 2 ∫ √(e^x-1) dx

let

e^(x/2) = seca

(1/2)e^(x/2) dx = (tana)^2 da

dx = 2(tana)^2/(seca) da

∫ √(e^x-1) dx

= ∫ tana [2(tana)^2/(seca) ]da

=2 ∫ (sina)^3/(cosa)^2 da

= -2∫ (1-(cosa)^2) / (cosa) ^2 dcosa

= 2 [ 1/cosa + cosa ] + C'

= 2[ e^(x/2) + e^(-x/2) ] + C'

∫x.e^x/ √(e^x-1) dx

= 2x√(e^x-1) - 2 ∫ √(e^x-1) dx

= 2x√(e^x-1) - 4 [ e^(x/2) + e^(-x/2) ] + C