Question

1. cosx=-3
2. 1+cos5x=1
3. cos (x-П/3)=1

Answer 1

1. cosx = -3 - не имеет решения, т.к. косинус аргумента принадлежит отрезку [-1; 1]

2. 1 + cos5x = 1
cos5x = 0
5x = π/2 + πn, n ∈ Z
x = π/10 + πn/5, n ∈ Z

3. cos(x - π/3) = 1
x - π/3 = 2πn, n ∈ Z
x = π/3 + 2πn, n ∈ Z.