ACOS (3)
arc cosine function
SYNOPSIS
#include <math.h>
double acos(double x );
DESCRIPTION
The acos() function calculates the arc cosine of x; that is
the value whose cosine is x. If x falls outside the range
-1 to 1, acos() fails and errno is set.
RETURN VALUE
The acos() function returns the arc cosine in radians and the
value is mathematically defined to be between 0 and PI (inclusive).
ERRORS
CONFORMING TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
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