# Exponential integral Ei(x)

## Calculates the exponential integral Ei(x).

 $Ei(x)=-{\large\int_{\small -x}^{\hspace{25}\small\infty}\frac{\large e^{-t}}{\large t}}dt$
 x
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 $\normal Exponential\ integral\ Ei(x)\\[10](1)\ Ei(x)=-{\large\int_{\small -x}^{\hspace{25}\small\infty}\frac{\large e^{-t}}{\large t}}dt\\(2)\ Ei(x)=\gamma+ln(x)+{\large\sum_{k=1}^{\infty}\frac{x^k}{kk!}} \hspace{20} x>0\\$

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