Question

prove that cos20.cos40.cos60.cos80=1/16

Answer 1

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!!!!!

Answer 2

Step-by-step explanation;

APPLY THE FORMULAE

cos(60+theta)  cos(theta) cos(60-theta)=1/4 sin(3 theta)

TAKE THETA WHICH IS SUITABLE FOR THIS EQUATION; 20

cos(20) cos(60-20) cos(60+20) cos 60

=1/4 cos(3 into 20) into 1/2

=1/4 cos 60 cos 60

=1/16