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ei

ei (x)​

The ei function returns the value of the exponential integral Ei (x):

Ei(x)=P∫−∞xettdt(x>0),\displaystyle E i(x)=P \int_{-\infty}^{x} \frac{e^{t}}{t} d t \quad(x>0),

where P denotes the principal value of the integral.

See Also​

expInt

References​

Abramowitz, M., and I.A. Stegun, "Handbook of Mathematical Functions", 228 pp., Dover, New York, 1972.