........................ (10)

   and

             ...................(11)

With some rearrangement equation 10 and 11 can be put together in the form

              ............... (12)

Equation 12 represents an equation of an ellipse with axis as E_x and E_y as shown in figure 3. The major (minor) axis of the ellipse making an angle of with E_x (E_y ) given by