changes.mady.by.user Arthur Aslanyan (Nafta College)
Saved on Mar 08, 2019
@wikipedia
Two different functions of real argument
{\rm Ei}(x) = - \int_{-x}^{\infty} \frac{e^{-\xi}}{\xi} \, d\xi
{\rm E_1}(x) = \int_{x}^{\infty} \frac{e^{-\xi}}{\xi} \, d\xi
...
