Calculate the arccosine.
double acos(
double x
);
float acos(
float x
); // C++ only
long double acos(
long double x
); // C++ only
float acosf(
float x
);
Parameters
- x
Value between –1 and 1 whose arccosine is to be calculated.
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 by default.
Input |
SEH Exception |
Matherr Exception |
|---|---|---|
± ∞ |
INVALID |
_DOMAIN |
± QNAN,IND |
none |
_DOMAIN |
|x|>1 |
INVALID |
_DOMAIN |
Remarks
C++ allows overloading, so you can call overloads of acos. In a C program, acos always takes and returns a double.
Requirements
Routine |
Required header |
Optional headers |
|---|---|---|
acos, acosf |
<math.h> |
<errno.h> |
Example
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.
// crt_asincos.c
// arguments: 0
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
int main( int ac, char* av[] )
{
double x,
y;
errno_t err;
// argument checking
if (ac != 2)
{
fprintf_s( stderr, "Usage: %s <number between -1 and 1>\n",
av[0]);
return 1;
}
// Convert argument into a double value
if ((err = sscanf_s( av[1], "%lf", &x )) != 1)
{
fprintf_s( stderr, "Error converting argument into ",
"double value.\n");
return 1;
}
// Arcsine of X
y = asin( x );
printf_s( "Arcsine of %f = %f\n", x, y );
// Arccosine of X
y = acos( x );
printf_s( "Arccosine of %f = %f\n", x, y );
}
Arcsine of 0.000000 = 0.000000
Arccosine of 0.000000 = 1.570796