Prove that `cos20^(@)cos40^(@)cos80^(@)=(1)/(8)`

Prove that cos 20^(@) cos 40^(@) cos 80^(@) = (1)/(8).

Prove that a) (sin3A + sinA)sinA+(cos3A-cosA) cosA=0 b) cos20^(@)cos40^(@)cos80^(@)=1/8

Prove that sin20^(@)sin40^(@)sin80^(@)=(sqrt(3))/(8)

Prove that: \ cos 20^0cos 40^0cos 80^0=1/8

Prove that: i) cos10^(@)cos30^(@)cos50^(@)cos70^(@)=3/16 ii) cos20^(@)cos40^(@)cos60^(@)cos80^(@)=1/16 iii) 4cos12^(@)cos48^(@)cos72^(@)=cos36^(@) iv) cos40^(@) cos80^(@)cos160^(@)=-1/8

Prove that cos12^(@)+cos84^(@)+cos132^(@)+cos156^(@)=-1/2

Prove that: cos20^0cos40^0cos60^0cos80^0=1/(16)

Prove that cos20^0cos40^0cos60^0cos80^0=1/(16)dot

Prove that sin 20^(@) sin 40^(@) sin 80^(@) = (sqrt3)/(8).

Prove that: cos 80^0+cos 40^0-cos 20^0=0