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