A=0; B=0; C=0;for j=1:nA=A+(cos(seta(j)))^2/D(j)^2*sigma(j)^2;B=B+sin(seta(j))*cos(seta(j))/D(j)^2*sigma(j)^2;C=C+(sin(seta(j)))^2/D(j)^2*sigma(j)^2;end
