13.3.4.7 Hyperbolic Sine and Cosine Integrals
The hyperbolic sine and cosine integrals are defined in the fashion of regular sine and cosine integrals. The hyperbolic sine integral is traditionally written as Shi(x) and is defined as given below.
The cosine hyperbolic function is represented as Chi(x) and is defined using the following formula.
Just like the sine and cosine integrals, the sine and cosine hyperbolic functions are used in number theory, quantum field theory and semi-conductor physics. The Math::Cephes function that returns a list containing both Shi(x) and Chi(x) for an given argument is called shichi.