In this chapter we present elementary algorithms to solve two basic numerical problems: evaluating the values of a function and of its derivative at a gine point. This problems will give the reader a hint of how Numerical Analysis works.The two cases illustrated in this chapter show that there can be many inequivalent algorithms to evaluate numerically the same "continuous" quantity and how critical is the choice of the appropriate one depending on the goals one needs to reach. Numerical Analysis is the part of Mathematics that studies and analyzes these algorithms.
