atan(), atanf(), atanl()

Compute the arctangent of an angle

Synopsis:

#include <math.h>

double atan( double x );

float atanf( float x );

long double atanl( long double x );

Arguments:

x
The tangent for which you want to find the angle.

Library:

libm

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

Description:

These functions compute the arctangent (in radians) of x.

Returns:

The arctangent, in the range (-π/2, π/2). For finite values of |x| > 1, these functions return NaN. The return value for ±Inf is NaN.

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

Errors:

FE_UNDERFLOW
The x argument is subnormal.

Examples:

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

int main( void )
{
    int except_flags;

    feclearexcept(FE_ALL_EXCEPT);

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

    except_flags = fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW);
    if(except_flags) {
        /* An error occurred; handle it appropriately. */
    }

    return EXIT_SUCCESS;
}

produces the output:

0.463648

Classification:

ANSI, POSIX 1003.1

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