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

theorem Th116: :: REAL_1'41_1
  b <> 0 & d <> 0 implies a / b + c / d =(a * d + c * b) / (b * d )
proof
  assume
A1: b<>0;
  assume d<>0;
  hence a/b + c/d=(a*d)/(b*d) + c/d by Lm10
    .=(a*d)/(b*d) + (c*b)/(b*d) by A1,Lm10
    .=(a*d + c*b)/(b*d) by Th62;
end;
