8. 4 tg (arccos (-1) + arccos √2/2)

1) $$arccos(-1) = \pi$$

2) $$arccos(\frac{\sqrt{2}}{2}) = \frac{\pi}{4}$$

3) $$\pi + \frac{\pi}{4} = \frac{5\pi}{4}$$

4) $$tg(\frac{5\pi}{4}) = 1$$

Ответ: 1