Equations (4.4) and (4.5) are symmetrical in a way that facilitates the writing of the equations. This symmetry also is present in the general case. For example, the coefficient of v2 in the first equation is the same as that of v1 in the second equation Also, the coefficient of v3 in the first equation is that of v1 in the third equation. Finally, the coefficient of v3 in the second equation is that of v2 in the third equation.These results follow from the fact that the conductance between nodes 1 and 2 is that between 2 and 1, the conductance between nodes 1 and 3 is that between 3 and 1, and so on.