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| 2 | /* @(#)w_acosh.c 5.1 93/09/24 */ |
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| 3 | /* |
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| 4 | * ==================================================== |
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 6 | * |
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 8 | * Permission to use, copy, modify, and distribute this |
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| 9 | * software is freely granted, provided that this notice |
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| 10 | * is preserved. |
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| 11 | * ==================================================== |
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| 12 | * |
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| 13 | */ |
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| 14 | |
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| 15 | /* |
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| 16 | FUNCTION |
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| 17 | <<acosh>>, <<acoshf>>---inverse hyperbolic cosine |
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| 18 | |
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| 19 | INDEX |
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| 20 | acosh |
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| 21 | INDEX |
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| 22 | acoshf |
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| 23 | |
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| 24 | SYNOPSIS |
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| 25 | #include <math.h> |
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| 26 | double acosh(double <[x]>); |
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| 27 | float acoshf(float <[x]>); |
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| 28 | |
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| 29 | DESCRIPTION |
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| 30 | <<acosh>> calculates the inverse hyperbolic cosine of <[x]>. |
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| 31 | <<acosh>> is defined as |
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| 32 | @ifnottex |
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| 33 | . log(<[x]> + sqrt(<[x]>*<[x]>-1)) |
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| 34 | @end ifnottex |
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| 35 | @tex |
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| 36 | $$ln\Bigl(x + \sqrt{x^2-1}\Bigr)$$ |
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| 37 | @end tex |
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| 38 | |
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| 39 | <[x]> must be a number greater than or equal to 1. |
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| 40 | |
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| 41 | <<acoshf>> is identical, other than taking and returning floats. |
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| 42 | |
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| 43 | RETURNS |
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| 44 | <<acosh>> and <<acoshf>> return the calculated value. If <[x]> |
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| 45 | less than 1, the return value is NaN and <<errno>> is set to <<EDOM>>. |
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| 46 | |
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| 47 | You can change the error-handling behavior with the non-ANSI |
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| 48 | <<matherr>> function. |
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| 49 | |
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| 50 | PORTABILITY |
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| 51 | Neither <<acosh>> nor <<acoshf>> are ANSI C. They are not recommended |
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| 52 | for portable programs. |
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| 53 | |
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| 54 | |
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| 55 | QUICKREF |
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| 56 | ansi svid posix rentrant |
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| 57 | acos n,n,n,m |
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| 58 | acosf n,n,n,m |
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| 59 | |
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| 60 | MATHREF |
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| 61 | acosh, NAN, arg,DOMAIN,EDOM |
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| 62 | acosh, < 1.0, NAN,DOMAIN,EDOM |
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| 63 | acosh, >=1.0, acosh(arg),,, |
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| 64 | |
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| 65 | MATHREF |
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| 66 | acoshf, NAN, arg,DOMAIN,EDOM |
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| 67 | acoshf, < 1.0, NAN,DOMAIN,EDOM |
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| 68 | acoshf, >=1.0, acosh(arg),,, |
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| 69 | |
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| 70 | */ |
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| 71 | |
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| 72 | /* |
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| 73 | * wrapper acosh(x) |
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| 74 | */ |
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| 75 | |
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| 76 | #include "fdlibm.h" |
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| 77 | #include <errno.h> |
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| 78 | |
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| 79 | #ifndef _DOUBLE_IS_32BITS |
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| 80 | |
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| 81 | #ifdef __STDC__ |
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| 82 | double acosh(double x) /* wrapper acosh */ |
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| 83 | #else |
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| 84 | double acosh(x) /* wrapper acosh */ |
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| 85 | double x; |
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| 86 | #endif |
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| 87 | { |
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| 88 | #ifdef _IEEE_LIBM |
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| 89 | return __ieee754_acosh(x); |
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| 90 | #else |
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| 91 | double z; |
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| 92 | struct exception exc; |
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| 93 | z = __ieee754_acosh(x); |
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| 94 | if(_LIB_VERSION == _IEEE_ || isnan(x)) return z; |
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| 95 | if(x<1.0) { |
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| 96 | /* acosh(x<1) */ |
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| 97 | exc.type = DOMAIN; |
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| 98 | exc.name = "acosh"; |
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| 99 | exc.err = 0; |
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| 100 | exc.arg1 = exc.arg2 = x; |
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| 101 | exc.retval = 0.0/0.0; |
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| 102 | if (_LIB_VERSION == _POSIX_) |
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| 103 | errno = EDOM; |
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| 104 | else if (!matherr(&exc)) { |
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| 105 | errno = EDOM; |
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| 106 | } |
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| 107 | if (exc.err != 0) |
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| 108 | errno = exc.err; |
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| 109 | return exc.retval; |
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| 110 | } else |
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| 111 | return z; |
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| 112 | #endif |
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| 113 | } |
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| 114 | |
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| 115 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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