高等数学积分求大神解一下 200
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let
t= atanu
dt = a(secu)^2 du
t=0, u=0
t=x/2, u=arcan[x/(2a)]
∫(-x/2->x/2) dt/(t^2+a^2)^(3/2)
=2∫(0->x/2) dt/(t^2+a^2)^(3/2)
=2∫(0->arcan[x/(2a)]) a(secu)^2 du/ (asecu)^3
=(2/a^2) ∫(0->arcan[x/(2a)]) cosu du
=(2/a^2) [sinu]| (0->arcan[x/(2a)])
=(2/a^2) [x/√(x^2+4a^2)]
t= atanu
dt = a(secu)^2 du
t=0, u=0
t=x/2, u=arcan[x/(2a)]
∫(-x/2->x/2) dt/(t^2+a^2)^(3/2)
=2∫(0->x/2) dt/(t^2+a^2)^(3/2)
=2∫(0->arcan[x/(2a)]) a(secu)^2 du/ (asecu)^3
=(2/a^2) ∫(0->arcan[x/(2a)]) cosu du
=(2/a^2) [sinu]| (0->arcan[x/(2a)])
=(2/a^2) [x/√(x^2+4a^2)]
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