The value of cos2A-B+cos2B-2cosA-BcosAcosB is
sinA
sin2A
cos2A
cosA
Explanation for correct option
The value of cos2A-B+cos2B-2cosA-BcosAcosB
=cosA-BcosA-B-2cosAcosB+cos2B=cosA-Bcos(A)cosB+sinAsinB-2cosAcosB+cos2B∵cosA-B=cosAcosB+sinAsinB=cosA-BsinAsinB-cosAcosB+cos2B=cosA-B-cosA+B+cos2B=-122cosA+BcosA-B+cos2B=-12cos2A+cos2B+cos2B=-122cos2A-1+2cos2B-1+cos2B=1-cos2B-cos2A+cos2B=1-cos2A=sin2A
Hence, the correct option is OptionB