Let (π)/2<θ<π and cot θ=-1/(2 √ 2). Then the value of sin ((15 θ)/2)( cos 8 θ+ sin 8 θ)+ cos ((15 θ)/2)( cos 8 θ- sin 8 θ) is equal to

Let $\displaystyle \frac{\pi}{2}<\theta<\pi$ and $\displaystyle \cot \theta=-\frac{1}{2 \sqrt{2}}$. Then the value of $\displaystyle \sin \left(\frac{15 \theta}{2}\right)(\cos 8 \theta+\sin 8 \theta)+\cos \left(\frac{15 \theta}{2}\right)(\cos 8 \theta-\sin 8 \theta)$ is equal to