# tan(), tanf(), tanl()

Calculate the tangent of an angle

## Synopsis:

```#include <math.h>

double tan( double x );

float tanf( float x );

long double tanl( long double x );
```

## Arguments:

x
The angle, in radians, for which you want to compute the tangent.

## Library:

libm

Use the -l m option to qcc to link against this library.

## Description:

These functions compute the tangent of x radians. A large magnitude argument may yield a result with little or no significance.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

• Call feclearexcept(FE_ALL_EXCEPT) before calling tan(), tanf(), or tanl().
• On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

## Returns:

The tangent value.

If x is: These functions return: Errors:
±0.0 x
±Inf NaN FE_INVALID
NaN NaN
Subnormal x
Note: The tangent function has mathematical poles at ..., -π/2, π/2, 3 * π/2, ..., but these numbers can't be expressed exactly in floating-point representation, so no FE_DIVBYZERO errors occur.

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

## Examples:

```#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
{
int except_flags;

feclearexcept(FE_ALL_EXCEPT);

printf( "%f\n", tan(.5) );

except_flags = fetestexcept(FE_ALL_EXCEPT);
if(except_flags) {
/* An error occurred; handle it appropriately. */
}

return EXIT_SUCCESS;
}
```

produces the output:

```0.546302
```

## Classification:

Safety:
Cancellation point No
Interrupt handler No
Signal handler No