Relative error between a real and complex number.

[Pacopag]

Homework Statement

So I've got a polynomial with real roots. It turns out that if you perturb one of the coefficients by a small amount, two of the roots end up in the complex plane. Now I want to find the relative error in my computation. For two real numbers, say x1 and x2, I would take
$$rel.err. = {{x1-x2}\over{x1}}$$.
But what do I do if x1 is real and x2 is complex?

Homework Equations

The Attempt at a Solution

 

[olgranpappy]

Homework Statement

So I've got a polynomial with real roots. It turns out that if you perturb one of the coefficients by a small amount, two of the roots end up in the complex plane. Now I want to find the relative error in my computation. For two real numbers, say x1 and x2, I would take
$$rel.err. = {{x1-x2}\over{x1}}$$.
But what do I do if x1 is real and x2 is complex?

Homework Equations

The Attempt at a Solution

mabye try
$$\frac{|x_1-x_2|}{x_1}$$

 

[Pacopag]

Yes. That makes sense. It is the distance between the two values. Works in the complex plane too. Thanks.