1 @cindex exponential integrals
2 @cindex integrals, exponential
4 Information on the exponential integrals can be found in Abramowitz &
5 Stegun, Chapter 5. These functions are declared in the header file
6 @file{gsl_sf_expint.h}.
9 * Exponential Integral::
11 * Hyperbolic Integrals::
13 * Trigonometric Integrals::
14 * Arctangent Integral::
17 @node Exponential Integral
18 @subsection Exponential Integral
19 @cindex E1(x), E2(x), Ei(x)
21 @deftypefun double gsl_sf_expint_E1 (double @var{x})
22 @deftypefunx int gsl_sf_expint_E1_e (double @var{x}, gsl_sf_result * @var{result})
23 These routines compute the exponential integral @math{E_1(x)},
27 E_1(x) := \Re \int_1^\infty dt \exp(-xt)/t.
34 E_1(x) := \Re \int_1^\infty dt \exp(-xt)/t.
39 @comment Domain: x != 0.0
40 @comment Exceptional Return Values: GSL_EDOM, GSL_EOVRFLW, GSL_EUNDRFLW
43 @deftypefun double gsl_sf_expint_E2 (double @var{x})
44 @deftypefunx int gsl_sf_expint_E2_e (double @var{x}, gsl_sf_result * @var{result})
45 These routines compute the second-order exponential integral @math{E_2(x)},
49 E_2(x) := \Re \int_1^\infty dt \exp(-xt)/t^2.
56 E_2(x) := \Re \int_1^\infty dt \exp(-xt)/t^2.
61 @comment Domain: x != 0.0
62 @comment Exceptional Return Values: GSL_EDOM, GSL_EOVRFLW, GSL_EUNDRFLW
65 @deftypefun double gsl_sf_expint_En (int @var{n}, double @var{x})
66 @deftypefunx int gsl_sf_expint_En_e (int @var{n}, double @var{x}, gsl_sf_result * @var{result})
67 These routines compute the exponential integral @math{E_n(x)} of order @math{n},
71 E_n(x) := \Re \int_1^\infty dt \exp(-xt)/t^n.
78 E_n(x) := \Re \int_1^\infty dt \exp(-xt)/t^n.
83 @comment Domain: x != 0.0
84 @comment Exceptional Return Values: GSL_EDOM, GSL_EOVRFLW, GSL_EUNDRFLW
91 @deftypefun double gsl_sf_expint_Ei (double @var{x})
92 @deftypefunx int gsl_sf_expint_Ei_e (double @var{x}, gsl_sf_result * @var{result})
93 These routines compute the exponential integral @math{Ei(x)},
97 Ei(x) := - PV\left(\int_{-x}^\infty dt \exp(-t)/t\right)
104 Ei(x) := - PV(\int_@{-x@}^\infty dt \exp(-t)/t)
109 where @math{PV} denotes the principal value of the integral.
110 @comment Domain: x != 0.0
111 @comment Exceptional Return Values: GSL_EDOM, GSL_EOVRFLW, GSL_EUNDRFLW
115 @node Hyperbolic Integrals
116 @subsection Hyperbolic Integrals
117 @cindex hyperbolic integrals
121 @deftypefun double gsl_sf_Shi (double @var{x})
122 @deftypefunx int gsl_sf_Shi_e (double @var{x}, gsl_sf_result * @var{result})
123 These routines compute the integral @math{Shi(x) = \int_0^x dt \sinh(t)/t}.
124 @comment Exceptional Return Values: GSL_EOVRFLW, GSL_EUNDRFLW
128 @deftypefun double gsl_sf_Chi (double @var{x})
129 @deftypefunx int gsl_sf_Chi_e (double @var{x}, gsl_sf_result * @var{result})
130 These routines compute the integral @math{ Chi(x) := \Re[ \gamma_E + \log(x) + \int_0^x dt (\cosh[t]-1)/t] }, where @math{\gamma_E} is the Euler constant (available as the macro @code{M_EULER}).
131 @comment Domain: x != 0.0
132 @comment Exceptional Return Values: GSL_EDOM, GSL_EOVRFLW, GSL_EUNDRFLW
139 @deftypefun double gsl_sf_expint_3 (double @var{x})
140 @deftypefunx int gsl_sf_expint_3_e (double @var{x}, gsl_sf_result * @var{result})
141 These routines compute the third-order exponential integral
142 @math{Ei_3(x) = \int_0^xdt \exp(-t^3)} for @c{$x \ge 0$}
144 @comment Exceptional Return Values: GSL_EDOM
147 @node Trigonometric Integrals
148 @subsection Trigonometric Integrals
149 @cindex trigonometric integrals
152 @deftypefun double gsl_sf_Si (const double @var{x})
153 @deftypefunx int gsl_sf_Si_e (double @var{x}, gsl_sf_result * @var{result})
154 These routines compute the Sine integral
155 @math{Si(x) = \int_0^x dt \sin(t)/t}.
156 @comment Exceptional Return Values: none
160 @deftypefun double gsl_sf_Ci (const double @var{x})
161 @deftypefunx int gsl_sf_Ci_e (double @var{x}, gsl_sf_result * @var{result})
162 These routines compute the Cosine integral @math{Ci(x) = -\int_x^\infty dt
163 \cos(t)/t} for @math{x > 0}.
164 @comment Domain: x > 0.0
165 @comment Exceptional Return Values: GSL_EDOM
169 @node Arctangent Integral
170 @subsection Arctangent Integral
171 @cindex arctangent integral
172 @deftypefun double gsl_sf_atanint (double @var{x})
173 @deftypefunx int gsl_sf_atanint_e (double @var{x}, gsl_sf_result * @var{result})
174 These routines compute the Arctangent integral, which is defined as @math{AtanInt(x) = \int_0^x dt \arctan(t)/t}.
176 @comment Exceptional Return Values: