13.3.4.3 Exponential Integral

Submitted by admin on Fri, 2007-11-16 11:36

13.3.4.3  Exponential Integral

The exponential integral is defined as

 

                     

The Equation Error! Reference source not found. is not defined for x£0.

There is a second version of the exponential integral known as  defined as given below.

 

 

                     

In Equation Error! Reference source not found., both n and x must be positive. The Math::Cephes module allows us to compute values for both Ei(n) and . The integrals are called Ei and Expn, respectively in Math::Cephes.