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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "ASIN" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" asin 

.SH NAME

asin, asinf, asinl \- arc sine function

.SH SYNOPSIS

.LP

\fB#include <math.h>

.br

.sp

double asin(double\fP \fIx\fP\fB);

.br

float asinf(float\fP \fIx\fP\fB);

.br

long double asinl(long double\fP \fIx\fP\fB);

.br

\fP

.SH DESCRIPTION

.LP

These functions shall compute the principal value of the arc sine

of their argument \fIx\fP. The value of \fIx\fP should be in

the range [-1,1].

.LP

An application wishing to check for error situations should set \fIerrno\fP

to zero and call

\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.

On return, if \fIerrno\fP is non-zero or

\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)

is non-zero, an error has occurred.

.SH RETURN VALUE

.LP

Upon successful completion, these functions shall return the arc sine

of \fIx\fP, in the range [-pi/2,pi/2] radians.

.LP

For finite values of \fIx\fP not in the range [-1,1], a domain error

shall occur, and   \ either a NaN

(if supported), or  \ an implementation-defined value shall be

returned.

.LP

If

\fIx\fP is NaN, a NaN shall be returned.

.LP

If \fIx\fP is \(+-0, \fIx\fP shall be returned.

.LP

If \fIx\fP is \(+-Inf, a domain error shall occur, and either a NaN

(if supported), or an implementation-defined value

shall be returned.

.LP

If \fIx\fP is subnormal, a range error may occur and \fIx\fP should

be returned. 

.SH ERRORS

.LP

These functions shall fail if:

.TP 7

Domain\ Error

The \fIx\fP argument is finite and is not in the range [-1,1],   \ or

is \(+-Inf.  

.LP

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,

then \fIerrno\fP shall be set to [EDOM]. If the

integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,

then the invalid floating-point exception shall be

raised.

.sp

.LP

These functions may fail if:

.TP 7

Range\ Error

The value of \fIx\fP is subnormal. 

.LP

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,

then \fIerrno\fP shall be set to [ERANGE]. If the

integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,

then the underflow floating-point exception shall be

raised. 

.sp

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.LP

None.

.SH APPLICATION USAGE

.LP

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling

& MATH_ERREXCEPT) are independent of

each other, but at least one of them must be non-zero.

.SH RATIONALE

.LP

None.

.SH FUTURE DIRECTIONS

.LP

None.

.SH SEE ALSO

.LP

\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIisnan\fP() , \fIsin\fP()

, the Base Definitions volume of

IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions

for

Mathematical Functions, \fI<math.h>\fP

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group. In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.opengroup.org/unix/online.html .