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+.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
+.TH "TAN" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
+.\" tan 
+.SH NAME
+tan, tanf, tanl \- tangent function
+.SH SYNOPSIS
+.LP
+\fB#include <math.h>
+.br
+.sp
+double tan(double\fP \fIx\fP\fB);
+.br
+float tanf(float\fP \fIx\fP\fB);
+.br
+long double tanl(long double\fP \fIx\fP\fB);
+.br
+\fP
+.SH DESCRIPTION
+.LP
+These functions shall compute the tangent of their argument \fIx\fP,
+measured in radians.
+.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 tangent
+of \fIx\fP.
+.LP
+If the correct value would cause underflow, and is not representable,
+a range error may occur, and   \ either 0.0 (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 subnormal, a range error may occur and \fIx\fP should
+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 the correct value would cause underflow, and is representable,
+a range error may occur and the correct value shall be
+returned. 
+.LP
+If the correct value would cause overflow, a range error shall occur
+and \fItan\fP(), \fItanf\fP(), and \fItanl\fP() shall
+return \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL, respectively,
+with the same sign as the correct value of the
+function. 
+.SH ERRORS
+.LP
+These functions shall fail if:
+.TP 7
+Domain\ Error
+The value of \fIx\fP 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.
+.TP 7
+Range\ Error
+The result overflows 
+.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 overflow floating-point exception shall be raised.
+.sp
+.LP
+These functions may fail if:
+.TP 7
+Range\ Error
+The result underflows,   \ or 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
+.SS Taking the Tangent of a 45-Degree Angle
+.sp
+.RS
+.nf
+
+\fB#include <math.h>
+\&...
+double radians = 45.0 * M_PI / 180;
+double result;
+\&...
+result = tan (radians);
+\fP
+.fi
+.RE
+.SH APPLICATION USAGE
+.LP
+There are no known floating-point representations such that for a
+normal argument, \fItan\fP( \fIx\fP) is either overflow or
+underflow.
+.LP
+These functions may lose accuracy when their argument is near a multiple
+of pi/2 or is far
+from 0.0.
+.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
+\fIatan\fP() , \fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIisnan\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 .