function Lambda=Evaluate_Transformation_Matrix(Length,iEnd,Nodes)
                                                                                                  
node_j=iEnd(1);
node_k=iEnd(2);
%
xk=Nodes{node_k}.x;
xj=Nodes{node_j}.x;
%
yk=Nodes{node_k}.y;
yj=Nodes{node_j}.y;

Dx=xk-xj;
Dy=yk-yj;

cosf=Dx/Length;
sinf=Dy/Length;

Lambda=[cosf sinf       0     0;
                -sinf cosf       0    0;
                      0     0 cosf sinf;
                      0     0 -sinf cosf];
                                                                                                  
                                                                                                  
end