Модуль cosx-0.5 модуль закрывается -sinx=0.5

COSx>1/2  cosx-0,5-sinx=1/2 cosx-sinx=1
                                             1-2sinxcosx=1
                                             sin2x=0
                                            x=пk/2
-п/3+2Пk<=x<=П/3+2пk
x=2Пk
cosx<1/2 0,5-cosx-sinx=1/2
                   cosx=-sinx
                  tgx=-1 x=-п/4+пk
П/3+2Пk<x<5П/3+2Пk
x=-П/4+(2k+1)П