tan(), tanf(), tanl()

Updated: May 06, 2022

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
The general-purpose math library.
libm-sve
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.

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:

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:

C11, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes