Q.13. Find the value of cos 2 20 ° cos 2 70 ° sin 2 31 ° sin 2 59 ° + sin 2 64 ° + cos 64 ° . sin 26 ° Share with your friends Share 1 Shruti Tyagi answered this Dear student, Assuming the question is cos220+cos270sin231+sin259+sin264+cos64.sin26 and solving furtherWe havecos220+cos270sin231+sin259+sin264+cos64.sin26=cos220+cos290-20sin231+sin290-31+sin264+cos64.sin90-64=cos220+sin220sin231+cos231+sin264+cos64.cos64 --[using sin (90-θ)=cosθ and cos(90-θ )=sinθ ]=11+sin264+cos264 --[using sin2θ+cos2θ=1]=1+1 --[using sin2θ+cos2θ=1] =2 Regards 0 View Full Answer