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acos, acosf
[arc cosine]

SYNOPSIS

    #include <math.h>
    double acos(double x);
    float acosf(float x);

DESCRIPTION

acos computes the inverse cosine (arc cosine) of the input value. Arguments to acos must be in the range of -1 to 1.

acosf is identical to acos, except that it performs its calculations on floats.

RETURNS

acos and acosf return values in radians, in the range of 0 to .

If x is not between -1 and 1, the returned value is NaN (not a number) the global variable errno is set to EDOM, and a DOMAIN error message is sent as standard error output.

You can modify error handling for these functions using matherr.