acos, acosf
Calculates the arccosine.
double acos( double x ); float acos( float x ); // C++ only long double acos( long double x ); // C++ only float acosf( float x );
Parameter
- 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 | Compatibility |
|---|---|---|---|
| acos, acosf | <math.h> | <errno.h> | ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP |
For additional compatibility information, see Compatibility in the Introduction.
Libraries
All versions of the C run-time libraries.
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;
if (ac != 2) {
fprintf(stderr, "Usage: %s <number between -1 and 1>\n", av[0]);
return 1;
}
sscanf( av[1], "%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
Arcsine of 0.000000 = 0.000000 Arccosine of 0.000000 = 1.570796
See Also
Floating-Point Support Routines | asin | atan, cos | _matherr | sin | tan | Run-Time Routines and .NET Framework Equivalents
