{{alias}}( x )
    Compute the arccosine of a number.

    Parameters
    ----------
    x: number
        Input value.

    Returns
    -------
    y: number
        Arccosine (in radians).

    Examples
    --------
    > var y = {{alias}}( 1.0 )
    0.0
    > y = {{alias}}( 0.707 )
    ~0.7855
    > y = {{alias}}( NaN )
    NaN

    See Also
    --------