Cos theta -2sin theta cos theta =0
cos(Ф) - 2sin(Ф).cos(Ф) =0Factorize--> cos(Ф)[ 1-2sin(Ф)] =0a) cos(Ф) = 0 ==> Ф= 0 or (0+2kπ)b) 1-2sin(Ф) =0 ==> -2sin(Ф) = - 1 ==> sin(Ф) =1/2 Orsin(Ф) = 1/2 ==> Ф =π/3 OR π/3 + (k+1)π/3
