'\" t .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk .\" .\" .\" 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 2024-05-02 "Linux man-pages 6.8" .SH NAME tan, tanf, tanl \- tangent function .SH LIBRARY Math library .RI ( libm ", " \-lm ) .SH SYNOPSIS .nf .B #include .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)