prove `cos 65^o + cos 115^o`=0

Prove that cos65^0+cos115^0=0

Prove that cos65^0+cos115^0=0

Prove that cos65^0+cos115^0=0

Prove that cos65^(@)+cos115^(0)=0

Prove that: cos 55^0+cos 65^0+cos 175^0=0

Prove tha sin 25^0 cos 115^0 = 1/2 (sin 140^0 -1)

Prove that: sin 65^0+cos 65^0=sqrt(2)cos 20^0

Without taking the help of the table of trigonometric ratios,show that:(iii) sin140^@cos65^@+cos50^@cos115^@=0

In o+ABC, prove that cos A+cos B+cos C<=(3)/(2)

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