а) cos t = $$\frac{1}{2}$$
t = ±arccos $$\frac{1}{2}$$ + 2$$\pi$$k, k ∈ Z
t = ±$$\frac{\pi}{3}$$ + 2$$\pi$$k, k ∈ Z
Ответ: t = ±$$\frac{\pi}{3}$$ + 2$$\pi$$k, k ∈ Z