cos2x=-1/2
2x=+-arccos (-1/2)+2πk k∈Z
Т.к. arccos(-a)+arcos (a)=π ⇒arccos(-1/2)=π-arccos(1/2)=π-π/3=2/3π
2x=+-2π/3+2πk x=+-(π/3)+πk k∈Z
cos2x=-1/2
2x=+-arccos (-1/2)+2πk k∈Z
Т.к. arccos(-a)+arcos (a)=π ⇒arccos(-1/2)=π-arccos(1/2)=π-π/3=2/3π
2x=+-2π/3+2πk x=+-(π/3)+πk k∈Z