function k=isci_theta_k(b,B);
  %ISCI_THETA doloci theta^*, resitev g(theta)=0
  %k=ISCI_THETA(b,B);
  f=inline('1-cos(theta)+B/b*(theta-sin(theta))','theta','b','B');
  %fplot(f,[0,2*pi],[],[],[],b,B);%[] morajo biti kot 'placeholderji'
  grid on;
  opt=optimset('fzero');
  k=fzero(f,atan(-b/B)+pi,opt,b,B); %za zacetni priblizek vzamemo drugo niclo drugega
                            %odvoda theta_0=atan(-b/B)+pi