The law of correspondence is the modern definition for the subject of functions. In addition, it is important to define concepts of domain and image, already explained in the function introduction post, under the vision of René Descartes. Tribute to Abel Niels Henrik Abel, from a large and poor family, was the son of the shepherd from the small village of Findo, in Norway. At the age of 17, his teacher insisted that he read the great mathematical works, including Gauss’s “Disquisitiones” (Research). At this time, Abel managed to generalize the binomial theorem that Euler had only proven for rational powers.