Function: If A and B are two non-empty sets, then a function from A to B, denoted as f(.): A→ B is a rule, which associates to each element x∊A to a unique element y∊B. The element y is called the image of x and written as y=f(x) is called a pre-image of y. The set is called the domain of f(.) and B its codomain or counter domain.
