127. б) arccos \frac{\sqrt{2}}{2} - arcsin (-1);

б) arccos $$\frac{\sqrt{2}}{2}$$ - arcsin(-1) = $$\frac{\pi}{4} - (-\frac{\pi}{2})$$ = $$\frac{\pi}{4} + \frac{\pi}{2}$$ = $$\frac{\pi + 2\pi}{4}$$ = $$\frac{3\pi}{4}$$.

Ответ: $$\frac{3\pi}{4}$$