Inverse trigonometric cosine of x.

In mathematics, this may be written as \(\arccos x\) or \(\cos^{-1}x\).

The returned value is in the interval \([0, \frac12\tau]\), and NA for the values of x that lie outside the interval [-1, 1]. This function is the inverse of cos() in the sense that cos(arccos(x)) == x for all x in the interval [-1, 1].

See also

  • cos(x) – the trigonometric cosine function;

  • arcsin(x) – the inverse sine function.