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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* arccosin function
* ________
* / 1 - x
* acos(x) = 2*atan2( / -------- , 1 )
* \/ 1 + x
*
* ________
* / 1 - x
* = 2*atan ( / -------- ) for non-exceptional x.
* \/ 1 + x
*
* Special cases:
* if x is NaN, return x itself;
* if |x|>1, return NaN with invalid signal.
*/
#pragma weak acosl = __acosl
#include "libm.h"
static const long double zero = 0.0L, one = 1.0L;
long double
acosl(long double x) {
if (isnanl(x))
return (x + x);
else if (fabsl(x) < one)
x = atanl(sqrtl((one - x) / (one + x)));
else if (x == -one)
x = atan2l(one, zero); /* x <- PI */
else if (x == one)
x = zero;
else { /* |x| > 1 create invalid signal */
return (zero / zero);
}
return (x + x);
}
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