MR-177. problem
1+ctg 2x·ctg xtgx + ctg x
1+ctg 2x·ctg xtgx + ctg x
=1+cos2xsin2x·cosxsinxsinxcosx+cosxsinx
=sin2x·sinx+cos2x·cosxsin2x·sinxsin2x+cos2xsinx·cosx
=cos2x-xsin2x·sinx1sinx·cosx
=cosxsin2x·sinx1sinx·cosx
=sinx·cos2xsin2x·sinx
=sinx·cos2x2sinx·cosx·sinx
=sinx·cos2x2sinx·cosx·sinx
=cosx2sinx
=12cosxsinx
=12ctg x
sin2α=2·sinα·cosα
sin2α=2·sinα·cosα
sin2α=2·sinα·cosα
1+ctg2x·ctgxtg x+ctgx=12·ctg x