`cos1^o +cos3^o +cos^5o +….+cos177^o +cos179^o `is,

sin15^o +cos15^o is:

cos210^o=

cos120^o=

Show that cos10^o cos30^o cos50^o cos70^o =3/16

Show that cos20^o cos40^o cos60^o cos80^o =1/16

The value of cos1^o.cos2 ^o.cos3^o.....cos179^o is equal to

Show that (cos15^o -cos105^o )/(cos15^o +cos105^o)=sqrt3

Prove that 16.Cos20^o . Cos40^o . Cos60^o. Cos80^o = Sin^2 100^o + Cos^2 100^o .

Evaluate the following: (i) sec50^osin40^o + cos40^o\ cos e c\ 50^o (ii) sec70^osin20^o-cos20^o\ cos e c\ 70^o

Prove that sin75^o -sin15^o =cos105^o +cos15^o