# Check if the function is odd or even

1. Dec 20, 2008

### transgalactic

i know that if f(x)=f(-x) and if f(-x)=-f(x) then its odd.

i tried to do this check on this cases
but its not working

http://img126.imageshack.us/img126/3942/74448798fv8.gif [Broken]

Last edited by a moderator: May 3, 2017
2. Dec 20, 2008

### Hootenanny

Staff Emeritus
These questions aren't always straight forward, you need to understand how the functions behave. Let's consider the first case:

So you have

$$f\left(-x\right) = \log\left(\frac{1+x}{1-x}\right) = \log\left(\frac{1-x}{1+x}\right)^{-1} = - \log\left(\frac{1-x}{1+x}\right) = -f\left(x\right)$$

Do you follow?

3. Dec 20, 2008

### HallsofIvy

Staff Emeritus
And, of course, most functions are neither even nor odd.

4. Dec 20, 2008

thanks