1 /* poly/zsolve_quadratic.c
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 /* complex_solve_quadratic.c - finds complex roots of a x^2 + b x + c = 0 */
24 #include <gsl/gsl_complex.h>
25 #include <gsl/gsl_poly.h>
28 gsl_poly_complex_solve_quadratic (double a, double b, double c,
29 gsl_complex *z0, gsl_complex *z1)
31 double disc = b * b - 4 * a * c;
33 if (a == 0) /* Handle linear case */
41 GSL_REAL(*z0) = -c / b;
51 double s = fabs (0.5 * sqrt (disc) / a);
59 double sgnb = (b > 0 ? 1 : -1);
60 double temp = -0.5 * (b + sgnb * sqrt (disc));
83 GSL_REAL (*z0) = -0.5 * b / a;
86 GSL_REAL (*z1) = -0.5 * b / a;
93 double s = fabs (0.5 * sqrt (-disc) / a);
95 GSL_REAL (*z0) = -0.5 * b / a;
98 GSL_REAL (*z1) = -0.5 * b / a;