Identity FunctionsThe function f is called the identity function if each element of set A has an image on itself i.e. f (a) = a ∀ a ∈ A. It is denoted by I. Example: The function f is an identity function as each element of A is mapped onto itself. The function f is a oneone and onto Invertible (Inverse) FunctionsA function f: X → Y is invertible if and only if it is a bijective function. Consider the bijective (one to one onto) function f: X → Y. As f is a one to one, therefore, each element of X corresponds to a distinct element of Y. As f is onto, there is no element of Y which is not the image of any element of X, i.e., range = codomain Y. The inverse function for f exists if f^{1} is a function from Y to X. Example: The inverse function of f is shown in fig:
Next TopicComposition of Functions

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