  In dealing with nonlinear systems, it is common to use numerical solutions.
Unlike the careful behavior towards the numerical results in chaotic regions,
the validity of numerical results in regions of transient chaos might not
always be taken into consideration. This article demonstrates that using
numerical methods to solve systems undergoing transient chaos can be
challenging and sometimes unreliable. To illustrate this issue, we use the
Lorenz system [1] in the region of transient chaos as an example. We show how
the result of the computation might completely change when using different
mathematically equivalent expressions. This raises the question of which result
should be relied on. To answer this question, we propose a method based on the
Lyapunov exponent to determine the reliability of the numerical solution and
apply it to the provided example. In fact, this method checks a necessary
condition for the validity of the numerical solution. Then, by increasing the
precision to the extent suggested by our method, we show that the result of our
studied case passes this test. In the end, we briefly discuss the scope and
limits of our method.
