Question

Prove: cos 20 cos 40 cos 60 cos 80 = 1/16

Answer 1

cos60° cos60°cos80°
1/2×1/2×1/4
1/16=1/16 proved.......

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!!!!!