Lecture
This lecture covers the concepts of restriction, prolongation, and graph of a function, focusing on the relationship between two functions f and g, where g is a restriction of f. It explains how to define a function by its graph, emphasizing the importance of understanding the graph as the set of all points (x, y) where y is the image of x under the function. The lecture also discusses the significance of the graph in representing a function visually and how it can be used to analyze and interpret the behavior of the function.