Again, we note that we
cannot draw the graph of the function without
lifting the pen This is yet another instance of
a function being not continuous at x = 0 Naively, we may say that a function is
continuous at a fixed point if we can draw the
graph of the function around that point without
lifting the pen from the plane of the paper Mathematically, it may be phrased precisely as follows:
Definition 1 Suppose f is a real function on a subset of the real numbers and let  c be
a point in the domain of f