acos

Calculates the arccosine.

doubleacos(doublex**);**

For additional compatibility information, see Compatibility in the Introduction.

Libraries

Return Value

The acos function returns the arccosine of x in the range 0 to π radians. If x is less than –1 or greater than 1, acos returns an indefinite (same as a quiet NaN). You can modify error handling with the _matherr routine.

Parameter

x

Value between –1 and 1 whose arccosine is to be calculated

Example

/* ASINCOS.C: This program prompts for a value in the range
 * -1 to 1. Input values outside this range will produce
 * _DOMAIN error messages.If a valid value is entered, the
 * program prints the arcsine and the arccosine of that value.
 */

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

void main( void )
{
   double x, y;

   printf( "Enter a real number between -1 and 1: " );
   scanf( "%lf", &x );
   y = asin( x );
   printf( "Arcsine of %f = %f\n", x, y );
   y = acos( x );
   printf( "Arccosine of %f = %f\n", x, y );
}

Output

Enter a real number between -1 and 1: .32696
Arcsine of 0.326960 = 0.333085
Arccosine of 0.326960 = 1.237711

Floating-Point Support Routines

See Also   asin, atan, cos, _matherr, sin, tan