2.2. cos(x - \frac{\pi}{4}) = -\frac{\sqrt{2}}{2};

2.2. cos($$\frac{1}{2}$$x -$$\frac{\pi}{4}$$) =-$$\frac{\sqrt{2}}{2}$$

$$\frac{1}{2}$$x -$$\frac{\pi}{4}$$ = arccos(-$$\frac{\sqrt{2}}{2}$$)

$$\frac{1}{2}$$x -$$\frac{\pi}{4}$$ =$$\frac{3\pi}{4}$$ + 2$$\pi$$n, n$$\isin$$Z

$$\frac{1}{2}$$x =$$\frac{3\pi}{4}$$ +$$\frac{\pi}{4}$$ + 2$$\pi$$n, n$$\isin$$Z

$$\frac{1}{2}$$x =$$\pi$$ + 2$$\pi$$n, n$$\isin$$Z

x=2$$\pi$$ + 4$$\pi$$n, n$$\isin$$Z

$$\frac{1}{2}$$x -$$\frac{\pi}{4}$$ =-$$\frac{3\pi}{4}$$ + 2$$\pi$$n, n$$\isin$$Z

$$\frac{1}{2}$$x =-$$\frac{3\pi}{4}$$ +$$\frac{\pi}{4}$$ + 2$$\pi$$n, n$$\isin$$Z

$$\frac{1}{2}$$x =-$$\frac{\pi}{2}$$ + 2$$\pi$$n, n$$\isin$$Z

x=-$$\pi$$ + 4$$\pi$$n, n$$\isin$$Z

Ответ: x=2$$\pi$$ + 4$$\pi$$n, x=-$$\pi$$ + 4$$\pi$$n, n$$\isin$$Z