# tan man page

tan, tanf, tanl — tangent function

## Synopsis

**#include <math.h>**
**double tan(double** *x***);**
**float tanf(float** *x***);**
**long double tanl(long double** *x***);**

`Link with `

*-lm*.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):**tanf**(), **tanl**():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

## Description

These functions return the tangent of *x*, where *x* is given in radians.

## Return Value

On success, these functions return the tangent of *x*.

If *x* is a NaN, a NaN is returned.

If *x* is positive infinity or negative infinity, a domain error occurs, and a NaN is returned.

If the correct result would overflow, a range error occurs, and the functions return **HUGE_VAL**, **HUGE_VALF**, or **HUGE_VALL**, respectively, with the mathematically correct sign.

## Errors

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

- Domain error:
*x*is an infinity *errno*is set to**EDOM**(but see Bugs). An invalid floating-point exception (**FE_INVALID**) is raised.- Range error: result overflow
- An overflow floating-point exception (
**FE_OVERFLOW**) is raised.

## Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |
---|---|---|

tan(), tanf(), tanl() | Thread safety | MT-Safe |

## Conforming to

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning *double* also conforms to SVr4, 4.3BSD, C89.

## Bugs

Before version 2.10, the glibc implementation did not set *errno* to **EDOM** when a domain error occurred.

## See Also

acos(3), asin(3), atan(3), atan2(3), cos(3), ctan(3), sin(3)

## Colophon

This page is part of release 4.09 of the Linux *man-pages* project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

## Referenced By

acos(3), asin(3), atan(3), atan2(3), cos(3), sin(3), sincos(3).

tanf(3) and tanl(3) are aliases of tan(3).