def atan(x):
    """ tan(x)
    Trigonometric arc tan function.
    """
    _math = infer_math(x)
    if _math is math:
        return _math.atan(x)
    else:
        return _math.arctan(x)
def atan ( x ) : _math = infer_math ( x ) if _math is math : return _math . atan ( x ) else : return _math . arctan ( x )
tan(x)
    Trigonometric arc tan function.