5sin2x+7-11cosx-11sinx=0 (5sin2x+5)+2-11cosx-11sinx=0 {sin2x+1=c0s^2x+2sinxcosx+sin^2x=(cosx+sinx)^2} 5(sin2x+1)-11(cosx+sinx)+2=0 5(cosx+sinx)^2-11(cosx+sinx)+2=0 cosx+sinx=t 5t^2-11t+2=0 D=81 далше сами решайте