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<cmath>
double acos ( double x );
float acos ( float x );
long double acos ( long double x );
Compute arc cosine
Returns the principal value of the arc cosine of x, expressed in radians.
In trigonometrics, arc cosine is the inverse operation of cosine.
In C++, this function is overloaded in <valarray> (see valarray acos).
Parameters
- x
- Floating point value in the interval [-1,+1].
If the argument is out of this interval, a domain error occurs, setting the global variable errno to the value EDOM.
Return Value
Principal arc cosine of x, in the interval [0,pi] radians.
Portability
In C, only the double version of this function exists with this name.
Example
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/* acos example */
#include <stdio.h>
#include <math.h>
#define PI 3.14159265
int main ()
{
double param, result;
param = 0.5;
result = acos (param) * 180.0 / PI;
printf ("The arc cosine of %lf is %lf degrees.\n", param, result );
return 0;
}
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Output:
The arc cosine of 0.500000 is 60.000000 degrees.
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See also
| cos | Compute cosine (function) |
| asin | Compute arc sine (function) |
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