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+'\" t
+.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\"     <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.\" References consulted:
+.\"     Linux libc source code
+.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
+.\"     386BSD man pages
+.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
+.\" Modified 2002-07-27 by Walter Harms
+.\" 	(walter.harms@informatik.uni-oldenburg.de)
+.\"
+.TH tan 3 (date) "Linux man-pages (unreleased)"
+.SH NAME
+tan, tanf, tanl \- tangent function
+.SH LIBRARY
+Math library
+.RI ( libm ", " \-lm )
+.SH SYNOPSIS
+.nf
+.B #include <math.h>
+.P
+.BI "double tan(double " x );
+.BI "float tanf(float " x );
+.BI "long double tanl(long double " x );
+.fi
+.P
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.P
+.BR tanf (),
+.BR tanl ():
+.nf
+    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
+        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
+        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.SH DESCRIPTION
+These functions return the tangent of
+.IR x ,
+where
+.I x
+is
+given in radians.
+.SH RETURN VALUE
+On success, these functions return the tangent of
+.IR x .
+.P
+If
+.I x
+is a NaN, a NaN is returned.
+.P
+If
+.I x
+is positive infinity or negative infinity,
+a domain error occurs,
+and a NaN is returned.
+.P
+If the correct result would overflow,
+a range error occurs,
+and the functions return
+.BR HUGE_VAL ,
+.BR HUGE_VALF ,
+or
+.BR HUGE_VALL ,
+respectively, with the mathematically correct sign.
+.\" I think overflow can't occur, because the closest floating-point
+.\" representation of pi/2 is still not close enough to pi/2 to
+.\" produce a large enough value to overflow.
+.\" Testing certainly seems to bear this out.  -- mtk, Jul 08
+.\"
+.\" POSIX.1 allows an optional underflow error;
+.\" glibc 2.8 doesn't do this
+.\" POSIX.1 an optional range error for subnormal x;
+.\" glibc 2.8 doesn't do this
+.SH ERRORS
+See
+.BR math_error (7)
+for information on how to determine whether an error has occurred
+when calling these functions.
+.P
+The following errors can occur:
+.TP
+Domain error: \fIx\fP is an infinity
+.I errno
+is set to
+.B EDOM
+(but see BUGS).
+An invalid floating-point exception
+.RB ( FE_INVALID )
+is raised.
+.TP
+Range error: result overflow
+.\" Unable to test this case, since the best approximation of
+.\" pi/2 in double precision only yields a tan() value of 1.633e16.
+.\" .I errno
+.\" is set to
+.\" .BR ERANGE .
+An overflow floating-point exception
+.RB ( FE_OVERFLOW )
+is raised.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.na
+.nh
+.BR tan (),
+.BR tanf (),
+.BR tanl ()
+T}	Thread safety	MT-Safe
+.TE
+.SH STANDARDS
+C11, POSIX.1-2008.
+.SH HISTORY
+C99, POSIX.1-2001.
+.P
+The variant returning
+.I double
+also conforms to
+SVr4, 4.3BSD, C89.
+.SH BUGS
+Before glibc 2.10, the glibc implementation did not set
+.\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
+.I errno
+to
+.B EDOM
+when a domain error occurred.
+.SH SEE ALSO
+.BR acos (3),
+.BR asin (3),
+.BR atan (3),
+.BR atan2 (3),
+.BR cos (3),
+.BR ctan (3),
+.BR sin (3)