2.5. cos($$\frac{1}{2}$$x -$$\frac{\pi}{6}$$) =$$\frac{1}{2}$$
$$\frac{1}{2}$$x -$$\frac{\pi}{6}$$ = arccos($$\frac{1}{2}$$)
$$\frac{1}{2}$$x -$$\frac{\pi}{6}$$ =$$\frac{\pi}{3}$$ + 2$$\pi$$n, n$$\isin$$Z
$$\frac{1}{2}$$x =$$\frac{\pi}{3}$$ +$$\frac{\pi}{6}$$ + 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
$$\frac{1}{2}$$x -$$\frac{\pi}{6}$$ =-$$\frac{\pi}{3}$$ + 2$$\pi$$n, n$$\isin$$Z
$$\frac{1}{2}$$x =-$$\frac{\pi}{3}$$ +$$\frac{\pi}{6}$$ + 2$$\pi$$n, n$$\isin$$Z
$$\frac{1}{2}$$x =-$$\frac{\pi}{6}$$ + 2$$\pi$$n, n$$\isin$$Z
x=-$$\frac{\pi}{3}$$ + 4$$\pi$$n, n$$\isin$$Z
Ответ: x =$$\pi$$ + 4$$\pi$$n, x=-$$\frac{\pi}{3}$$ + 4$$\pi$$n, n$$\isin$$Z