double E1(double X);
Exponential integral E1(x) = -Ei(-x).
| # | Name | Type | Description |
|---|---|---|---|
| 1 | X | double | Argument of the exponential integral; must be greater than zero. |
Returns: the exponential integral E1(x) = -Ei(-x).
Remarks:
Computes the exponential integral of the first kind,
E_1(x)=integral _x^(inf)(e^(-t))/t dt=-Ei(-x),
defined and positive for x > 0, decreasing monotonically from +\infty at x\to 0^+ toward 0 as x\to\infty (asymptotically e^{-x}/x). Domain: real x > 0.
See Also: SpecialFuncs::EI, SpecialFuncs::ExpEI
Declared in Dew::Math::Units::SpecialFuncs · Dew.Math/Units.SpecialFuncs.h · Cross-compiler