请问1/(1+tanx)的不定积分怎么求?
2个回答

∫1/(1+tanx)dx

=∫1/(1+sinx/cosx)dx

=∫cosx/(cosx+sinx)dx

=∫cosx(cosx-sinx)/(cosx+sinx)(cosx-sinx)dx

=∫(cos²x-sinxcosx)/(cos²x-sin²x)dx

=[∫(1+cos2x-sin2x)/cos2xdx]/2

=[∫(1+cos2x-sin2x)/cos2xd2x]/4

=(∫sec2xd2x+∫d2x+∫tan2xd2x)/4

=ln|sec2x+tan2x|/4+x/2+ln|cos2x|/4+C

=x/2+ln|cos2x(sec2x+tan2x)|/4+C

=x/2+ln(1+sin2x)/4+C