`cos80^(@)+cos40^(@)-cos20^(@)=0`

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

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

Prove that cos 20^(@) cos 40^(@) cos 80^(@) = (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

Evaluate : sin50^(@)cos40^(@)+cos40^(@)+cos50^(@)sin40^(@)

Simplify be reducing to a single term : sin 80^(@) cos 20^(@) - cos 80^(@) sin 20^(@).

Prove that : (i) sin42^(@)cos48^(@)+sin48^(@)cos42^(@)=1 (ii) cos70^(@)cos20^(@)-sin70^(@)sin20^(@)=0

Statement-1: cos10^(@)+cos20^(@)+…..+cos170^(@)=0 Statement-2: cos alpha+cos(alpha+beta)+....+cos(alpha+(n-1)beta)=(cos(alpha+((n-1)beta)/(2))sin((nbeta)/(2)))/(sin((beta)/(2))), beta ne 2npi.

Value of cos0^(@). Cos 30^(@) . cos45^(@) . cos60^(@) . Cos90^(@) is __________.

Prove that : "cosec "65^(@)cos25^(@)+"cosec20"^(@)cos70^(@)=2