Arc cosine

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double acos(double x);

[Return value]

Returns the arc cosine of x. The returned value is in radian and in a range of 0 to .

If x is not between -1 and 1, a Not a Nuber(NaN) is returned, and macro EDOM is set to global variable errno.

[Description]

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