  We are introducing two methods for revealing the true inflection point of
data that contains or not error. The starting point is a set of geometrical
properties that follow the existence of an inflection point p for a smooth
function. These properties connect the concept of convexity/concavity before
and after p respectively with three chords defined properly. Finally a set of
experiments is presented for the class of sigmoid curves and for the third
order polynomials.
