Question

Find the value of cos 20 cos 40 cos 60 cos 80

Answer 1

cos 20° cos 40° cos 80°
let, 20°=x
•.•cos x cos 2x cos 4x=1/3 cos 3x
=1/3 cos 3×20°
=1/3 cos 60°
=(1/3)(1/2)
=1/6 Answer

Answer 2

DEAR STUDENT,

Kindly check the attached papers for a detailed solution along with step by step elaboration to reach our final solution that is our final desired or required answer to this query that is completely proved.

$\boxed{\bf{\underline{L.H.S. = R.H.S.}}}$

Which is the required proof or solution process for this type of query.

Hope this helps you and solves your doubts for applying trigonometric identifies to reach a proper solution or a proof!!!!!