How to prove these equations base on this following interior and exterior angle bisectors problem?

Question

In the triangle $\triangle ABC$, length of $BC$ is larger than length of $AC$.

The interior angle bisector of $\angle C$ intersects $AB$ at $D$; and the exterior angle bisector of $\angle C$ intersects the extension of $AB$ at $E$.

How to prove that:

$$|DE|= \frac{2abc}{a^2-b^2}$$

Thanks