2. Обчислити: 1) arctg 1 - arctg (-1);

Математика. $$arctg(1) - arctg(-1) = \frac{\pi}{4} - (-\frac{\pi}{4}) = \frac{\pi}{4} + \frac{\pi}{4} = \frac{2\pi}{4} = \frac{\pi}{2}$$ Ответ: $$\frac{\pi}{2}$$