acos(), acosf(), acosl()

Compute the arccosine of an angle

Synopsis:

#include <math.h>

double acos( double x );

float acosf( float x );

long double acosl( long double x );

Arguments:

x
The cosine 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 arccosine (in radians) of x.

Returns:

The arccosine in the range (0, π). For finite values not in the range [-1,1], these functions return NaN. The return value for ±Inf is NaN.

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

Errors:

FE_INVALID
|x| isn't less than or equal to 1.0, or x is ±Inf or NaN.

Examples:

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

int main( void )
{
    int except_flags;

    feclearexcept(FE_ALL_EXCEPT);

    printf( "acos(0.5) is %f\n", acos(0.5) );

    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:

1.047197

Classification:

ANSI, POSIX 1003.1

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