Ответ:

[tex] \frac{2\pi}{3} [/tex]

Объяснение:

[tex]arccos( - 1) - arctg( \sqrt{3} ) = \\ = \pi - \frac{1}{3} \pi = \\ = \pi - \frac{\pi}{3} = \\ = \frac{3\pi - \pi}{3} = \\ = \frac{2\pi}{3} [/tex]