# Manual Reference Pages  - TAN (3)

### NAME

tan, tanf, tanl - tangent function

Synopsis
Description
Return Value
Errors
Bugs
Colophon

### 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():

_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

### DESCRIPTION

The tan() function returns 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.

### CONFORMING TO

C99, POSIX.1-2001. 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 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

 TAN (3) 2010-09-11
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