Equation Icon  A = Ax(x)t3 dx + (A1(x)t1 + A2(x)t2)dz + (A3(x)t1 + A4(x)t2) df, (54) x -@- 1 2 @-- 3 4 -@- E = E (x)t3@x + (E (x)t1 + E (x)t2) @z + (E (x)t1 + E (x)t2)@f (55)