Exponential Integrals¶
Exponential Integral¶
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gsl_sf_expint_E1(x)¶
This routine computes the exponential integral \(\operatorname{E_1}(x)\),
\[\operatorname{E_1}(x) := \operatorname{Re} \int_1^\infty \exp(-xt)/t dt.\]
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gsl_sf_expint_E2(x)¶
This routine computes the second-order exponential integral \(\operatorname{E_2}(x)\),
\[\operatorname{E_2(x)} := \operatorname{Re} \int_1^\infty \exp(-xt)/t^2 dt.\]
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gsl_sf_expint_En(n, x)¶
This routine computes the exponential integral \(\operatorname{E_n}(x)\) of order \(n\),
\[\operatorname{E_n}(x) := \operatorname{Re} \int_1^\infty \exp(-xt)/t^n dt.\]
Ei(x)¶
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gsl_sf_expint_Ei(x)¶
These routines compute the exponential integral \(\operatorname{Ei}(x)\),
\[\operatorname{Ei}(x) := - PV(\int_{-x}^\infty \exp(-t)/t dt)\]where \(PV\) denotes the principal value of the integral.
Hyperbolic Integrals¶
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gsl_sf_Shi(x)¶
This routine computes the integral
\[\operatorname{Shi}(x) = \int_0^x \sinh(t)/t dt.\]
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gsl_sf_Chi(x)¶
This routine computes the integral
\[\operatorname{Chi}(x) := \operatorname{Re}[ \gamma_E + \log(x) + \int_0^x (\cosh(t)-1)/t dt],\]where \(\gamma_E\) is the Euler constant.
Ei_3(x)¶
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gsl_sf_expint_3(x)¶
This routine computes the third-order exponential integral
\[\operatorname{Ei_3}(x) = \int_0^x \exp(-t^3) dt \text{ for } x \geq 0.\]
Trigonometric Integrals¶
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gsl_sf_Si(x)¶
This routine computes the Sine integral
\[\operatorname{Si}(x) = \int_0^x \sin(t)/t dt.\]
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gsl_sf_Ci(x)¶
This routine computes the Cosine integral
\[\operatorname{Ci}(x) = -\int_x^\infty \cos(t)/t dt \text{ for } x > 0.\]
Arctangent Integral¶
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gsl_sf_atanint(x)¶
This routine computes the Arctangent integral, which is defined as
\[\operatorname{AtanInt}(x) = \int_0^x \arctan(t)/t dt.\]