Are all functions odd or even?

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Discussion Overview

The discussion revolves around the classification of functions as odd or even, particularly in the context of Fourier Transforms. Participants explore whether all functions can be categorized as odd, even, both, or neither, and provide examples and definitions related to these properties.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that for Fourier Transforms, odd functions result in bn = 0 and even functions result in an = 0.
  • One participant defines even and odd functions, stating that an even function satisfies f(-x) = f(x) and an odd function satisfies f(-x) = -f(x).
  • A participant introduces the concept of decomposing a function into even and odd components using g(x) and h(x), showing that any function can be expressed in terms of these components.
  • Another participant provides an example of a function, f(x) = x + 1, to illustrate that it is neither even nor odd, as it does not satisfy the conditions for either classification.
  • It is mentioned that most functions are neither even nor odd, and a function can only be both if it is the zero function.
  • A participant states that the exponential function is neither odd nor even.

Areas of Agreement / Disagreement

Participants generally agree on the definitions of odd and even functions and the possibility of decomposing functions into these components. However, there is no consensus on whether all functions can be classified as odd or even, as multiple views and examples suggest that many functions are neither.

Contextual Notes

The discussion highlights the complexity of function classification and the conditions under which functions can be considered odd or even. There are unresolved aspects regarding specific functions and their properties.

Who May Find This Useful

This discussion may be useful for students and professionals in mathematics and physics, particularly those interested in function properties, Fourier analysis, and mathematical reasoning.

madmike159
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For functions when doing Fourier Transforms, when a function is odd bn = 0 and when a function is even an = 0.

Are all functions odd or even, or are there some cases where they're both / neither?
 
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An even function has the property:
f(-x)=f(x)

An odd function has the property:
f(-x)=-f(x)

Suppose you have a function f(x) that is neither odd nor even.

Now, define a function [tex]g(x)=\frac{f(x)+f(-x)}{2}[/tex].

So that, [tex]g(-x)=\frac{f(-x)+f(-(-x))}{2}=\frac{f(x)+f(-x)}{2}[/tex].

This means that g(x) is an even function, regardless of the properties of f(x)!

Similarly, let [tex]h(x)=\frac{f(x)-f(-x)}{2}[/tex].

It's easy to show that h(x) must be odd.

So, functions may be broken up into even and odd components.
 
Ok thanks.
 
For example, the function f(x)= x+ 1 has the property that f(2)= 3 while f(-2)= -1. Since neither f(2)= f(-2) nor f(2)= -f(-2) is true, this function is neither even nor odd.
In fact, most functions are neither even nor odd.

In order that a function be both even and odd, we would have to have both f(x)= f(-x) and f(x)= -f(-x) for all x. That is the same as saying f(x)= -f(-x)= -f(x) so that 2f(x)= 0 for all x. The is only true for the "zero" function, f(x)= 0 for all x.
 
the exp function is not odd nor even.
 

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