We are given a right-angled triangle where \( \angle C = 90^\circ \). Using the properties of the incenter and applying the standard formula for the incircles, we simplify the equation \( \left( \frac{I_1 - I_3}{I_1} \right) \left( \frac{I_2 - I_3}{I_2} \right) \) and obtain the value as 2.