1+cos5x=2cos5x/2
2cos²5x/2-2cos5x/2=0 ⇒2cos5x/2(cos5x/2-1)=0
cos5x/2=0 или cos5x/2=1
5x/2=π/2+πn,n∈z 5x/2=2πn,n∈z
5x=π+2πn,n∈z 5x=4πn,n∈z
x1=π/5+2πn/5,n∈z x2=4πn/5,n∈z
2)1-cosx=2sinx/2
2sin²x/2-2sinx/2=0
2sinx/2(sinx/2-1)=0
sinx/2=0 или sinx/2=1
x/2=πn,n∈z x/2=π/2+2πn,n∈z
x1=2πn,n∈z x2=π+4πn,n∈z