Trailing-Edge
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PDP-10 Archives
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SRI_NIC_PERM_FS_1_19910112
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kccdist/lib/pml/dasin.c
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/*
* +++ NAME +++
*
* DASIN Double precision arc sine
*
* +++ INDEX +++
*
* DASIN
* machine independent routines
* trigonometric functions
* math libraries
*
* +++ DESCRIPTION +++
*
* Returns double precision arc sine of double precision
* floating point argument.
*
* +++ USAGE +++
*
* double dasin(x)
* double x;
*
* +++ REFERENCES +++
*
* Fortran IV-plus user's guide, Digital Equipment Corp. pp B-2.
*
* +++ RESTRICTIONS +++
*
* For precision information refer to documentation of the floating
* point library primatives called.
*
* +++ PROGRAMMER +++
*
* Fred Fish
* Goodyear Aerospace Corp, Arizona Div.
* (602) 932-7000 work
* (602) 894-6881 home
*
* +++ INTERNALS +++
*
* Computes arcsine(X) from:
*
* (1) If X = 0.0 then DASIN(X) = 0.0
*
* (2) If X = 1.0 then DASIN(X) = PI/2.
*
* (3) If X = -1.0 then DASIN(X) = -PI/2
*
* (4) If -1.0 < X < 1.0 then
* DASIN(X) = DATAN(Y)
* Y = X / DSQRT[1-(X**2)]
*
* ---
*/
/*)LIBRARY
*/
#include <stdio.h>
#include "pmluse.h"
#include "pml.h"
double dasin(x)
double x;
{
double datan(), dsqrt();
if ( x > 1.0 || x < -1.0) {
pmlerr(DASIN_BADARG);
return(0.0);
} else if (x == 0.0)
return (0.0);
else if (x == 1.0)
return (HALFPI);
else if (x == -1.0)
return (-HALFPI);
else
return datan(x / dsqrt(1.0 - x * x));
}