changes.mady.by.user Arthur Aslanyan (Nafta College)
Saved on Mar 08, 2019
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Two different functions are called this way:
{\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
which are related to each other as: