Keil Logo


#include <math.h>

double acos (
  double x);   /* number to calculate arc cosine of */

The acos function calculates the arc cosine of the floating-point number x whose value must be between -1 and 1. The floating-point value returned by acos is a number in the range 0-π.

Return Value

The acos function returns the arc cosine of x.

For x ∈ [-1, 1], acos(x) → [0, π].
For x ∈ (-∞, -1) ∪ (1, ∞), acos(x)NaN.

See Also

asin, atan, atan2

#include <math.h>
#include <stdio.h> /* for printf */

void tst_acos (void) {
  float x;
  float y;

  for (x = -1.0; x <= 1.0; x += 0.1) {
    y = acos (x);
    printf ("ACOS(%f) = %f\n", x, y);
  Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.

Change Settings

Privacy Policy Update

Arm’s Privacy Policy has been updated. By continuing to use our site, you consent to Arm’s Privacy Policy. Please review our Privacy Policy to learn more about our collection, use and transfers
of your data.