Given a differentiable map "f" from R"m" into R"n", the critical points of "f" are the points of R"m", where the rank of the Jacobian matrix of "f" is not maximal. The image of a critical point under "f" is a called a critical value. A point in the complement of the set of critical values is called a regular value. Sard's theorem states that the set of critical values of a smooth map has measure zero. In particular, if "n" = 1, there is a finite number of critical values in each bounded interval.