84 lines
1.5 KiB
C
84 lines
1.5 KiB
C
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/* @(#)z_atan.c 1.0 98/08/13 */
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/*
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FUNCTION
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<<atan>>, <<atanf>>---arc tangent
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INDEX
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atan
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INDEX
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atanf
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ANSI_SYNOPSIS
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#include <math.h>
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double atan(double <[x]>);
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float atanf(float <[x]>);
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TRAD_SYNOPSIS
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#include <math.h>
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double atan(<[x]>);
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double <[x]>;
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float atanf(<[x]>);
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float <[x]>;
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DESCRIPTION
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<<atan>> computes the inverse tangent (arc tangent) of the input value.
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<<atanf>> is identical to <<atan>>, save that it operates on <<floats>>.
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RETURNS
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@ifnottex
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<<atan>> returns a value in radians, in the range of -pi/2 to pi/2.
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@end ifnottex
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@tex
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<<atan>> returns a value in radians, in the range of $-\pi/2$ to $\pi/2$.
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@end tex
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PORTABILITY
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<<atan>> is ANSI C. <<atanf>> is an extension.
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*/
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/******************************************************************
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* Arctangent
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*
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* Input:
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* x - floating point value
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*
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* Output:
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* arctan of x
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*
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* Description:
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* This routine returns the arctan of x.
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*
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*****************************************************************/
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#include "fdlibm.h"
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#include "zmath.h"
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#ifndef _DOUBLE_IS_32BITS
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double
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_DEFUN (atan, (double),
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double x)
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{
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switch (numtest (x))
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{
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case NAN:
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errno = EDOM;
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return (x);
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case INF:
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/* this should check to see if neg NaN or pos NaN... */
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return (__PI_OVER_TWO);
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case 0:
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return (0.0);
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default:
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return (atangent (x, 0, 0, 0));
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}
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}
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#endif /* _DOUBLE_IS_32BITS */
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