# tan (3)

# NAME

tan, tanf, tanl - tangent function# SYNOPSIS

#include <math.h>

Link withdouble tan(doublex);float tanf(floatx);long double tanl(long doublex);

*-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

|| /* 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)