<Li> if f ′ (x) is not zero, the point is a non-stationary point of inflection </Li> <P> A stationary point of inflection is not a local extremum . More generally, in the context of functions of several real variables, a stationary point that is not a local extremum is called a saddle point . </P> <P> An example of a stationary point of inflection is the point (0, 0) on the graph of y = x . The tangent is the x-axis, which cuts the graph at this point . </P> <P> An example of a non-stationary point of inflection is the point (0, 0) on the graph of y = x + ax, for any nonzero a . The tangent at the origin is the line y = ax, which cuts the graph at this point . </P>

When does a function have an inflection point