5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */

  25 /*
  26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29 
  30 /*
  31  * arccosin function
  32  *                            ________
  33  *                           / 1 - x
  34  *      acos(x) = 2*atan2(  / -------- , 1 )
  35  *                        \/   1 + x
  36  *
  37  *                            ________
  38  *                           / 1 - x
  39  *              = 2*atan (  / -------- ) for non-exceptional x.
  40  *                        \/   1 + x
  41  *
  42  * Special cases:
  43  *      if x is NaN, return x itself;
  44  *      if |x|>1, return NaN with invalid signal.
  45  */
  46 
  47 #pragma weak __acosl = acosl
  48 
  49 #include "libm.h"
  50 
  51 static const long double zero = 0.0L, one = 1.0L;
  52 
  53 long double
  54 acosl(long double x) {

  55         if (isnanl(x))
  56                 return (x + x);
  57         else if (fabsl(x) < one)
  58                 x = atanl(sqrtl((one - x) / (one + x)));
  59         else if (x == -one)
  60                 x = atan2l(one, zero);  /* x <- PI */
  61         else if (x == one)
  62                 x = zero;
  63         else {          /* |x| > 1  create invalid signal */
  64                 return (zero / zero);
  65         }
  66         return (x + x);
  67 }

   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 
  26 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 /*
  32  * arccosin function
  33  *                            ________
  34  *                           / 1 - x
  35  *      acos(x) = 2*atan2(  / -------- , 1 )
  36  *                        \/   1 + x
  37  *
  38  *                            ________
  39  *                           / 1 - x
  40  *              = 2*atan (  / -------- ) for non-exceptional x.
  41  *                        \/   1 + x
  42  *
  43  * Special cases:
  44  *      if x is NaN, return x itself;
  45  *      if |x|>1, return NaN with invalid signal.
  46  */
  47 
  48 #pragma weak __acosl = acosl
  49 
  50 #include "libm.h"
  51 
  52 static const long double zero = 0.0L, one = 1.0L;

  53 long double
  54 acosl(long double x)
  55 {
  56         if (isnanl(x))
  57                 return (x + x);
  58         else if (fabsl(x) < one)
  59                 x = atanl(sqrtl((one - x) / (one + x)));
  60         else if (x == -one)
  61                 x = atan2l(one, zero);  /* x <- PI */
  62         else if (x == one)
  63                 x = zero;
  64         else                            /* |x| > 1  create invalid signal */
  65                 return (zero / zero);
  66 
  67         return (x + x);
  68 }