int от 0 до pi/3 (cos(3x-(pi/6))dx=(1/3)*sin(3x-(pi/6)) от 0 до pi/3 =
= (1/3)*[sin(0-pi/6)-sin(pi/3-pi/6)]=(1/3)*sin(-pi/6)+(1/3)*sin(pi/6)=(1/3)*[(-1/2)-(1/2))=0
