Question

решите уравнение 4Cos²x-1=0

Answer 1

4cosx^2-1=0
(2cosx-1)(2cosx+1)=0
2cosx-1=0
cosx=1/2
x=+-pi/3+2pi*n, n∈Z
2cosx+1=0
cosx=-1/2
x=+-2pi/3+2pi*k, k∈Z