Format
#include <math.h>
double acos(double x);Language Level: ANSI
Threadsafe: Yes.
Description
The acos() function calculates the arccosine of x, expressed in radians, in the range 0 to Π.
Return Value
The acos() function 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 that uses acos()
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 <stdio.h>
#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: %lf too small for acos\n", x );
else {
y = acos( x );
printf( "acos( %lf ) = %lf\n", x, y );
}
}
/******* Expected output if 0.4 is entered: *********
Enter x
acos( 0.400000 ) = 1.159279
*/Related Information