Sin(x)^2 = cos(x/2)^2

First of all, you can use

and the equation becomes

Now, from the known identity

we can half all the angles and we get

So, the equation has become

So, everything comes down to solve

The associated equation

has roots

So, we want one of the following

Solve for the associated angles and you're done

1/2*qr*rs

step-by-step explanation: