求积分 ∫(arctanx)/(x^2(x^2+1))dx

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求积分∫(arctanx)/(x^2(x^2+1))dx求积分∫(arctanx)/(x^2(x^2+1))dx求积分∫(arctanx)/(x^2(x^2+1))dx∫(arctanx)/(x^2(

求积分 ∫(arctanx)/(x^2(x^2+1))dx
求积分 ∫(arctanx)/(x^2(x^2+1))dx

求积分 ∫(arctanx)/(x^2(x^2+1))dx
∫(arctanx)/(x^2(x^2+1))dx
let
x=tana
dx = (seca)^2da
∫(arctanx)/(x^2(x^2+1))dx
= ∫ [a/(tana)^2] da
=-∫ ad(cota+a)
= -a(cota+a) + ∫ (cota+a)da
= -a(cota+a) + ln|sina| + a^2/2 + C
=-arctanx( 1/x + arctanx) + ln|x/√(1+x^2) | + (arctanx)^2/2 + C
=-(1/x)arctanx -(arctanx)^2/2 +ln|x/√(1+x^2) |+ C