84 lines
1.3 KiB
C
84 lines
1.3 KiB
C
/*
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* (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
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* See the copyright notice in the ACK home directory, in the file "Copyright".
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*
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* Author: Ceriel J.H. Jacobs
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*/
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/* $Id$ */
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#include <math.h>
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#include <errno.h>
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extern int errno;
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static double
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asin_acos(x, cosfl)
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double x;
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{
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int negative = x < 0;
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int i;
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double g;
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extern double sqrt();
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static double p[] = {
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-0.27368494524164255994e+2,
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0.57208227877891731407e+2,
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-0.39688862997540877339e+2,
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0.10152522233806463645e+2,
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-0.69674573447350646411e+0
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};
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static double q[] = {
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-0.16421096714498560795e+3,
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0.41714430248260412556e+3,
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-0.38186303361750149284e+3,
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0.15095270841030604719e+3,
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-0.23823859153670238830e+2,
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1.0
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};
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if (negative) {
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x = -x;
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}
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if (x > 0.5) {
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i = 1;
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if (x > 1) {
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errno = EDOM;
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return 0;
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}
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g = 0.5 - 0.5 * x;
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x = - sqrt(g);
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x += x;
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}
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else {
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/* ??? avoid underflow ??? */
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i = 0;
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g = x * x;
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}
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x += x * g * POLYNOM4(g, p) / POLYNOM5(g, q);
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if (cosfl) {
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if (! negative) x = -x;
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}
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if ((cosfl == 0) == (i == 1)) {
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x = (x + M_PI_4) + M_PI_4;
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}
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else if (cosfl && negative && i == 1) {
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x = (x + M_PI_2) + M_PI_2;
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}
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if (! cosfl && negative) x = -x;
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return x;
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}
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double
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asin(x)
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double x;
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{
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return asin_acos(x, 0);
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}
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double
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acos(x)
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double x;
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{
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return asin_acos(x, 1);
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}
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