$1 + \cos 2x + \cos 4x + \cos 6x = $

$96 \cos \frac{\pi}{33} \cos \frac{2 \pi}{33} \cos \frac{4 \pi}{33} \cos \frac{8 \pi}{33} \cos \frac{16 \pi}{33}=...............$

${\cos ^2}\,{10^o}\,\, - \,\cos \,\,{10^o}\,\cos \,\,{50^o}\, + \,{\cos ^2}\,{50^o}$ ની કિમત ..... થાય.

જો $x + \frac{1}{x} = 2\,\cos \theta ,$ તો ${x^3} + \frac{1}{{{x^3}}} = $

 $(sinx + cosecx)^2 + (cosx + secx)^2 - ( tanx + cotx)^2$ =

સાબિત કરો કે : $\cos 4 x=1-8 \sin ^{2} x \cos ^{2} x$