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

theorem :: REAL_2'67_2
  a / b / c = 1 / b * (a / c)
proof
  a/b/c =a*b"/c by XCMPLX_0:def 9
    .=a*b"*c" by XCMPLX_0:def 9
    .=a*c"*b"
    .=a/c*b" by XCMPLX_0:def 9
    .=a/c/b by XCMPLX_0:def 9;
  hence a/b/c =b"*(a/c) by XCMPLX_0:def 9
    .=1/b*(a/c) by Lm4;
end;
