Show that x is independent of this trig expression For some reason I cannot get the solution.
Show that $x$ is independent of: $\sin^2(x+y)+\sin^2(x+z)-2\cos(y-z)\sin(x+y)\sin(x+z)$
I have used all the identities but seem to be missing something.

$\sin^2(x+y)+\sin^2(x+z) =1-[\cos^2(x+y)-\sin^2(x+z)]$
Using Prove that $\cos (A + B)\cos (A - B) = {\cos ^2}A - {\sin ^2}B$,
$\cos^2(x+y)-\sin^2(x+z)=\cos(2x+y+z)\cos(y-z)$
and then use Werner formula, for $2\sin(x+y)\sin(x+z)$
