1-sin(x/6)=cos(x/3)
x/3=2*(x/6)
cos(x/3)=cos(2*(x/3))=1-2sin²(x/6)
1-sin(x/6)=1-2sin²(x/6)
2sin²(x/6)-sin(x/6)=0
sin(x/6) *(2sin(x/6)-1)=0
1. sin(x/6)=0, x/6=πn, n∈Z
x₁=6πn, n∈Z
2. 2sin(x/6)-1=0
2sin(x/6)=1
sin(x/6)=1/2
x/6=(-1)^n *arcsun(1/2)+πn, n∈Z
x/6=(-1)^n *(π/6)+πn, n∈Z
x₂=(-1)^n*π+6πn, n∈Z