acosf(3)

acosf3

Arc cosine functions

Part of acos(3).

Usage

#include <math.h>

double

acos(double x);

float

acosf(float x);

long double

acosl(long double x);

Library

Math Library (libm, -lm)

Overview

The acos(), acosf(), and acosl() functions compute the principal value of the arc cosine of x.

Return values

These functions return the arc cosine in the range [0], radians. If:

|x| > 1,

acos(x) raises an invalid exception and returns an .

Releases

83 releases since FreeBSD 2.2.2-RELEASE; the text changed 45 times.

  1. 2.2.2–2.2.8
  2. 2.2.9
  3. 3.0–3.2
  4. 3.3–3.5.1
  5. 4.0–4.2
  6. 4.3
  7. 4.4
  8. 4.5–4.11
  9. 5.0–5.3
  10. 5.4–5.5
  11. 6.0–6.2
  12. 6.3
  13. 6.4
  14. 7.0
  15. 7.1
  16. 7.2
  17. 7.3
  18. 7.4
  19. 8.0
  20. 8.1
  21. 8.2
  22. 8.3
  23. 8.4
  24. 9.0
  25. 9.1
  26. 9.2
  27. 9.3
  28. 10.0
  29. 10.1
  30. 10.2
  31. 10.3
  32. 10.4
  33. 11.0
  34. 11.1
  35. 11.2
  36. 11.3
  37. 11.4
  38. 12.0
  39. 12.1
  40. 12.2
  41. 12.3
  42. 12.4
  43. 13.0
  44. 13.1–13.2
  45. 13.3–14.5
  46. 15.0–16.0

Standards

The acos(), acosf(), and acosl() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.