It is a point where function is neither maximum nor minimum.Geometrically such a surface forms a ridge rising in one direction & falling in another direction.
Statement:- It states that if a function f(x) is derivable in an interval [a,b], and also f(a)=f(b), then there exists at least one value ‘c' of x lying within [a,b] such that f'(c)=0.
The process in which we determine the lengths of arcs of plane curves whose equations are given in the cartesian, parametric or polar form is known as Rectification.