Cos(П/2-2Х/3)=sinП/3
cos((Pi/2)–(2х/3))=sin(2x/3) sin(Pi/3)=sqrt(3)/2 sin(2x/3)=sqrt(3)/2 (2x/3)=(-1)^(k)*(Pi/3)+Pik, k ∈ Z x=(-1)^(k)(Pi/2)+(3Pi/2)k, k ∈ Z О т в е т. (-1)^(k)(Pi/2)+(3Pi/2)k, k ∈ Z