reserve a, b, c, d, e for Complex;

theorem :: JGRAPH_2'1
  a <> 0 & b <> 0 implies (a / b) * (b / a) = 1
proof
  assume
A1: a<>0 & b<>0;
  (b/a)=(a/b)" by Lm7;
  hence thesis by A1,XCMPLX_0:def 7;
end;
