cos(x)cos(π/2) + sin(x)sin(π/2) =2sin(x)cos(x)
cos(π/2)=0
sin(π/2)=1
sin(x)=2sin(x)cos(x) ; 2sin(x)cos(x) - sin(x) =0
sin(x)[2cos(x) - 1] =0
1) sin(x) =0
x = [tex] (-1)^{k} arcsin0 + k \pi [/tex] unde k∈Z
2) 2cos(x) -1=0
cos(x) = 1/2
x= +- arccos1/2 + 2kπ = +- π/3 + 2kπ unde k∈Z
