>>970
∫{1/(1+tanx)}dx
=∫{cosx/(cosx+sinx)}dx
=∫{(cosx-sinx)/(cosx+sinx)}dx+∫{sinx/(cosx+sinx)}dx
=∫{(cosx-sinx)/(cosx+sinx)}dx+∫dx-{cosx/(cosx+sinx)}dx
=(1/2)∫{(cosx-sinx)/(cosx+sinx)}dx+(1/2)∫dx
=(1/2)log|cosx+sinx|+(1/2)x+C