Arc cosine

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double __far acos(double x);

[Return value]

Returns the arc cosine of x. The returned value is in radian and in a range of [0, π].

If x is not between [-1, 1], acos returns a Not-a-Number (NaN) and sets macro EDOM to global variable errno.

[Description]

This function calculates the arc cosine of x. Specify x as, -1<= x <= 1.