Konstruktive Methoden für den Aufbau des Grenzwertkonzepts

The author discusses some possibilities to let the class constructively pursue, already in early years of Italian secondary school, the way to limits. First, she describes the historic way of the theorem of zeros, and goes in the second part into alternative ways that make it possible to introduce the idea of limits slowly and gradually. The following examples are closer examined: Recurring decimals; the velocity in linear motions; the function y=(sin x)/x in a neighborhood of 0.