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

theorem :: REAL_2'91_1
  a / (2 * b) + a / (2 * b) = a / b
proof
  thus a/(2*b)+a/(2*b)=(a+a)/(2*b) by Th62
    .=2*a/(2*b)
    .=a/b by Lm10;
end;
