vector{f}=(1/(b-a)) ∫ ^(b)_(a)f(x)dx
vector{f}=(1/(4-3)) ∫ ^(4)_(3)(0,2·cos((2·pi/3)·x+(pi/2))dx
=0,2 ∫ ^(4)_(3)(-sin((2·pi/3)·x)dx=
=0,2*(3/2Pi)(cos(2·pi/3)·x)|^(4)_(3)=
=(0,3/Pi)*(cos(8Pi/3)-cos(2Pi))=
=(0,3/Pi)*(cos(2Pi/3)-cos(0))=
=(0,3/Pi)*(-1/2-1)=-9/(20Pi)