Function Composition

Definition

Function composition is the process of combining two or more functions to create a new function. The resulting function represents the combined effect of applying the individual functions in a specific order.

5 Must Know Facts For Your Next Test

1. Function composition is denoted by the symbol '$\circ$' and is read as 'composed with' or 'of'.
2. The order of function composition is important, as $(f\circ g)(x)$ is not the same as $(g\circ f)(x)$.
3. Function composition is a way to create new functions from existing ones, allowing for more complex mathematical modeling.
4. The domain of the composed function $(f\circ g)(x)$ is the set of all $x$ values for which $g(x)$ is in the domain of $f$.
5. The range of the composed function $(f\circ g)(x)$ is the set of all possible output values of $f(g(x))$.

Review Questions

• Explain how function composition relates to the concept of inverse functions.
  • Function composition is closely related to inverse functions. If $f$ and $g$ are functions such that $g = f^{-1}$, then $(f\circ g)(x) = (f\circ f^{-1})(x) = x$. This means that composing a function with its inverse function results in the identity function, which leaves the input unchanged. Conversely, if $(f\circ g)(x) = x$ for all $x$ in the domain of $g$, then $g$ must be the inverse function of $f$.
• Describe how function composition is used in the context of the limit laws (Section 2.3).
  • The limit laws, including the constant multiple rule, sum rule, difference rule, product rule, and quotient rule, can be extended to handle function composition. For example, the chain rule, which is covered in Section 3.6, allows us to find the derivative of a composed function by applying the product rule to the inner and outer functions. Understanding function composition is crucial for applying the limit laws to more complex functions involving multiple operations.
• Explain how the concept of function composition is related to the basic classes of functions discussed in Section 1.2.
  • The basic classes of functions, such as polynomial, rational, exponential, and trigonometric functions, can be combined through function composition to create more complex functions. For instance, composing a polynomial function with a trigonometric function can lead to functions that model periodic phenomena in the real world. Understanding function composition allows us to build and analyze a wider range of mathematical models by combining simpler functions in meaningful ways.

Related terms

Domain:

The set of input values for which a function is defined.

Range:

The set of all possible output values of a function.

Inverse Function:

A function that undoes the effect of another function, reversing the input-output relationship.