Proof That f(x) is 0 if Both Odd and Even

In summary, an even function is defined as f(-x) = f(x) and an odd function is defined as f(-x) = -f(x). If a function is both odd and even, it must be the constant function 0. This can be proven by using the definitions of even and odd functions and the fact that a square is always positive, leading to a contradiction if any other function is assumed to be both odd and even.
  • #1
STAR3URY
18
0

Homework Statement


Prove that if f(x) is both odd and even (functions) then f(x) must be the constant function 0. Basically prove that no other function other than 0, can be both odd and even.
 
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  • #2
How do you define an odd function and an even function?
 
  • #3
neutrino said:
How do you define an odd function and an even function?


Odd function is when f(-x) = -f(x) and even is if f(-x) = f(-x)
 
  • #4
STAR3URY said:
even is if f(-x) = f(-x)

That's not quite right.

But in a way, that is what you have to use once you have the definitions of both types of functions. :)
 
  • #5
As neutrino said, you got the definition wrong. Get the definition right, and then you can make progress.
 
  • #6
f(-x) = f(x) is even

f(-x) = -f(x) is odd
 
  • #7
The definitions are correct. Now if a function has to fullfill both of these, it fullfills the product. Use this together with the fact that a square is always... and the fact that something is positive and negative at the same time must be...
 
  • #8
Basically f(-x) = -f(-x) i.e. f = -f. The rest is algebra.
 

1. What is the definition of an odd function?

An odd function is a type of mathematical function where f(-x) = -f(x) for all values of x. This means that the function is symmetric about the origin and its graph is rotated 180 degrees around the origin.

2. What is the definition of an even function?

An even function is a type of mathematical function where f(-x) = f(x) for all values of x. This means that the function is symmetric about the y-axis and its graph remains unchanged when reflected over the y-axis.

3. How can a function be both odd and even?

If a function is both odd and even, it means that it satisfies both the conditions of an odd and even function. This can occur when the function is f(x) = 0, where f(-x) = -f(x) and f(-x) = f(x). In other words, the function is symmetric about both the origin and the y-axis.

4. What is the proof that f(x) is 0 if both odd and even?

The proof for this statement is based on the definition of an odd and even function. If a function is both odd and even, then f(-x) = -f(x) and f(-x) = f(x). By substituting f(x) = 0 into these equations, we get 0 = -0 and 0 = 0, which are both true. Therefore, if a function is both odd and even, it must be equal to 0.

5. Can a function be neither odd nor even?

Yes, a function can be neither odd nor even. This type of function is called an arbitrary function, which means that it does not satisfy the conditions of an odd or even function. In other words, the function is not symmetric about the origin or the y-axis and its graph is not rotated or reflected in any way.

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