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/* Translated into C++ by SciPy developers in 2024.
* Original header with Copyright information appears below.
*/
/* tandg.c
*
* Circular tangent of argument in degrees
*
*
*
* SYNOPSIS:
*
* double x, y, tandg();
*
* y = tandg( x );
*
*
*
* DESCRIPTION:
*
* Returns the circular tangent of the argument x in degrees.
*
* Range reduction is modulo pi/4. A rational function
* x + x**3 P(x**2)/Q(x**2)
* is employed in the basic interval [0, pi/4].
*
*
*
* ACCURACY:
*
* Relative error:
* arithmetic domain # trials peak rms
* IEEE 0,10 30000 3.2e-16 8.4e-17
*
* ERROR MESSAGES:
*
* message condition value returned
* tandg total loss x > 1.0e14 (IEEE) 0.0
* tandg singularity x = 180 k + 90 INFINITY
*/
/* cotdg.c
*
* Circular cotangent of argument in degrees
*
*
*
* SYNOPSIS:
*
* double x, y, cotdg();
*
* y = cotdg( x );
*
*
*
* DESCRIPTION:
*
* Returns the circular cotangent of the argument x in degrees.
*
* Range reduction is modulo pi/4. A rational function
* x + x**3 P(x**2)/Q(x**2)
* is employed in the basic interval [0, pi/4].
*
*
* ERROR MESSAGES:
*
* message condition value returned
* cotdg total loss x > 1.0e14 (IEEE) 0.0
* cotdg singularity x = 180 k INFINITY
*/
/*
* Cephes Math Library Release 2.0: April, 1987
* Copyright 1984, 1987 by Stephen L. Moshier
* Direct inquiries to 30 Frost Street, Cambridge, MA 02140
*/
#pragma once
#include "../config.h"
#include "../error.h"
namespace xsf {
namespace cephes {
namespace detail {
constexpr double tandg_lossth = 1.0e14;
XSF_HOST_DEVICE inline double tancot(double xx, int cotflg) {
double x;
int sign;
/* make argument positive but save the sign */
if (xx < 0) {
x = -xx;
sign = -1;
} else {
x = xx;
sign = 1;
}
if (x > detail::tandg_lossth) {
set_error("tandg", SF_ERROR_NO_RESULT, NULL);
return 0.0;
}
/* modulo 180 */
x = x - 180.0 * std::floor(x / 180.0);
if (cotflg) {
if (x <= 90.0) {
x = 90.0 - x;
} else {
x = x - 90.0;
sign *= -1;
}
} else {
if (x > 90.0) {
x = 180.0 - x;
sign *= -1;
}
}
if (x == 0.0) {
return 0.0;
} else if (x == 45.0) {
return sign * 1.0;
} else if (x == 90.0) {
set_error((cotflg ? "cotdg" : "tandg"), SF_ERROR_SINGULAR, NULL);
return std::numeric_limits<double>::infinity();
}
/* x is now transformed into [0, 90) */
return sign * std::tan(x * detail::PI180);
}
} // namespace detail
XSF_HOST_DEVICE inline double tandg(double x) { return (detail::tancot(x, 0)); }
XSF_HOST_DEVICE inline double cotdg(double x) { return (detail::tancot(x, 1)); }
} // namespace cephes
} // namespace xsf
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