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