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Computing › C › Math.h ›

acos

Arc cosine function
Contents
  1. Interface
  2. Description
  3. Special Values
  4. See Also
  5. Standards
  6. Compatibility
  7. Page Comments

Interface

#include <math.h>
double acos (double x)
long double acosl (long double x)
float acosf (float x)

#include <complex.h>
complex acos (complex x)
double complex cacos (double complex x)
float complex cacosf (float complex x)
long double complex cacosl (long double complex x)

Description

The acos function computes the principal value of the arc cosine of x in the range \inline [0, \pi]. acosl and acosf are the long double and the float versions, correspondingly.

The complex inverse cosine is defined by:
\mathrm{acos}(x) = -i \log \left( x+ i \sqrt{1-x^2} \right).
(1)

Example:
Example - Arc cosine function
Problem
This is an example of finding arc cosine of x
Workings
#include <stdio.h>
#include <math.h>
int main()
{
  double x = 0.5;
  double result = acos(x);
  printf("The arc cosine of %lf is %lf\n", x, result);
  return 0;
}
Solution
Output:

The arc cosine of 0.500000 is 1.047198

Special Values

acos ( 1 ) returns +0.
acos ( x ) returns a NaN and raises the invalid floating-point exception for |x| > 1.

See Also

reference:sin, reference:cos, reference:tan, reference:asin, reference:atan, reference:atan2, reference:sinh, reference:cosh, reference:tanh

Standards

The acos function conforms to ISO/IEC 9899:1999(E).

Compatibility

DOSUNIXWindowsANSI CC++ only
acosl••
Real acos••••
Complex acos•••
Complex cacos••
Last Modified: 22 Feb 12 @ 22:43     Page Rendered: 2021-12-22 02:03:40