Вычислите: 13.4. а) sin(-π/4) + cos(π/3) + cos(-π/6)

13.4. а) $\sin\left(-\frac{\pi}{4}\right) + \cos\frac{\pi}{3} + \cos\left(-\frac{\pi}{6}\right) = -\frac{\sqrt{2}}{2} + \frac{1}{2} + \frac{\sqrt{3}}{2} = \frac{1 + \sqrt{3} - \sqrt{2}}{2}$ б) $\cos\frac{\pi}{6} \cdot \cos\frac{\pi}{4} \cdot \cos\frac{\pi}{3} \cdot \cos\frac{\pi}{2} = \frac{\sqrt{3}}{2} \cdot \frac{\sqrt{2}}{2} \cdot \frac{1}{2} \cdot 0 = 0$ в) $\sin\left(-\frac{\pi}{2}\right) - \cos(-\pi) + \sin\left(-\frac{3\pi}{2}\right) = -1 - (-1) + 1 = -1 + 1 + 1 = 1$ г) $\sin\frac{\pi}{6} \cdot \sin\frac{\pi}{4} \cdot \sin\frac{\pi}{3} \cdot \sin\frac{\pi}{2} = \frac{1}{2} \cdot \frac{\sqrt{2}}{2} \cdot \frac{\sqrt{3}}{2} \cdot 1 = \frac{\sqrt{6}}{8}$ 13.5. а) $\sin\left(-\frac{3\pi}{4}\right) + \cos\left(-\frac{\pi}{4}\right) + \sin\frac{\pi}{4} \cdot \cos\frac{\pi}{2} + \cos 0 \cdot \sin\frac{\pi}{2} = -\frac{\sqrt{2}}{2} + \frac{\sqrt{2}}{2} + \frac{\sqrt{2}}{2} \cdot 0 + 1 \cdot 1 = 0 + 0 + 1 = 1$ б) $\cos\frac{5\pi}{3} + \cos\frac{4\pi}{3} + \sin\frac{3\pi}{2} \cdot \sin\frac{5\pi}{8} \cdot \cos\frac{3\pi}{2} = \frac{1}{2} + \left(-\frac{1}{2}\right) + (-1) \cdot \sin\frac{5\pi}{8} \cdot 0 = \frac{1}{2} - \frac{1}{2} + 0 = 0$