56. Вычислите: а) \(\sin\left(-\frac{3\pi}{4}\right)+\cos\left(-\frac{\pi}{4}\right)+\sin\frac{\pi}{4}\cdot\cos\frac{\pi}{2}+\cos0\cdot\sin\frac{\pi}{2}\); б) \(\(\cos\)\(\frac{5\pi}{3}\)+\(\cos\)\(\frac{4\pi}{3}\)+\(\sin\)\(\frac{3\pi}{2}\)\(\cdot\)\(\sin\)\(\frac{5\pi}{8}\)\(\cdot\)\(\cos\)\(\frac{3\pi}{2}\)\(\cdot [числовые данные обрезаны]\).