Show that cos2x - cos3x - cosx =0 For x= 2π/7 Share with your friends Share 0 Neha Sethi answered this Dear student cos2x-cos3x-cosx=cos2x-cos3x+cosx=cos2x-2cos3x+x2cos3x-x2 as cosA+cosB=2cosA+B2cosA-B2=cos2x-2cos2x cosx=cos2x(1-2cosx)=cos2×2π71-2cos2π7=cos4π71-2cos2π7Please recheck the question because for x=2π7 we cannot get the desired result. Regards 0 View Full Answer
