acos -- Calculate Arccosine

Format

#include <math.h>
double acos(double x);

Language Level: ANSI, POSIX, XPG4
acos calculates the arccosine of x, expressed in radians, in the range 0 to PI.

Return Value
acos returns the arccosine of x. The value of x must be between -1 and 1 inclusive. If x is less than -1 or greater than 1, acos sets errno to EDOM and returns 0.

Example
This example prompts for a value for x. It prints an error message if x is greater than 1 or less than -1; otherwise, it assigns the arccosine of x to y.

#include <stdlib.h>
#include <math.h>
#define MAX  1.0
#define MIN -1.0
int main(void)
{
  double x, y;
  printf( "Enter x\n" );
  scanf( "%lf", &x );
  /* Output error if not in range */
  if ( x > MAX )
    printf( "Error: %lf too large for acos\n", x );
  else
    if ( x < MIN )
       printf("Error: %If too small for acos\n",x);
    else {
       y = acos(x);
       printf("acos(%If) = %If\n", x, y);
    }
  return 0;
  /************************************************
     For the following input: 0.4
     The output should be:
     Enter x
     acos(0.400000) = 1.159279
  ************************************************/
}


asin -- Calculate Arcsine
atan - atan2 -- Calculate Arctangent
cos -- Calculate Cosine
cosh -- Calculate Hyperbolic Cosine
_facos -- Calculate Arccosine
_fcos -- Calculate Cosine
_fcossin -- Calculate Cosine and Sine
_fsincos -- Calculate Sine and Cosine
sin -- Calculate Sine
sinh -- Calculate Hyperbolic Sine
tan -- Calculate Tangent
tanh -- Calculate Hyperbolic Tangent
<math.h>