Question 1179609
.
<pre>

The product to sum formula, relevant to this case, is


    {{{sin(a)*sin(b) = (1/2)*(cos(a-b) - cos(a+b))}}}.



In the formula, use  a= 4theta,  b= 2theta.   You will get


    {{{sin(a)*sin(b)}}} = {{{(1/2)*(cos(4theta-2theta) - cos(4theta+2theta))}}},

or

    {{{sin(a)*sin(b)}}} = {{{(1/2)*(cos(2theta) - cos(6theta))}}}.


It is your <U>ANSWER</U>
</pre>

Solved, answered, explained and completed.