Решите уравнение cos2x=-1/2

Question

Решите уравнение cos2x=-1/2

Answer 1

cos2x=-1/2

2х =  ±2П/3 + 2Пn,     nєZ

х =  ±2П/6 + 2Пn/2,     nєZ

х =  ±П/3 + Пn,     nєZ

 

Answer 2

cos2x=-1/2

 

2x = ±2pi/3 +2pik   /:2

 

x = ±pi/3 +pik, k∈Z