Suppose f(⋅)  is a continuous function over a closed and bounded interval [a, b]. Then there exists a point d in [a, b] where f(⋅) has a minimum, and a point c in [a, b] where f(⋅) has a maximum, so that f(d) ≤ f(x) ≤ f(c) for all x in [a, b]. The statement is derived from: