# Fourier Transformations

1. Mar 5, 2009

### skaboy607

Can anyone explain the above-i've read about in books, internet sites and still do not understand what its doing or the maths.

Thanks

2. Mar 5, 2009

### mathman

Try wikipedia. It can't be explained in a few sentences.

3. Mar 5, 2009

### skaboy607

hmm, ive read that and although i understand the basic, i.e complicated function and representing with smaller functions with sin and cosine waves, the rest doesn't make sense no matter how many times I read it.

4. Mar 5, 2009

### ice109

how old are you? what level mathematical maturity do you have?

5. Mar 5, 2009

### skaboy607

Not really sure why it matters but im 21. hmmm not that much i guess?

6. Mar 5, 2009

### ice109

you know anything about vectors? how you can express any vector as a sum of basis vectors?

7. Mar 5, 2009

### skaboy607

hmmm cant say that I do, is that where I should start then?

8. Mar 5, 2009

### ice109

what do you know then? why do you want to know about fourier transforms?

9. Mar 6, 2009

### yyat

An intuitive explanation:
I am sure you have seen one of these http://en.wikipedia.org/wiki/Spectral_analyzer" [Broken] found on Hi-Fi's or digital audio players, that plot frequency vs. amplitude. They take the audio signal (amplitude/time), apply the (discrete) Fourier transform, and display the resulting function (amplitude/frequency).

To illustrate, take the function $$\cos(2\pi at)$$, which is a wave with frequency $$a$$. Its Fourier transform is zero except for two "spikes" at $$-a$$ and $$a$$.

A more mathematical reason why the Fourier transform is important, is that it turns differentiation into multiplication, see http://en.wikipedia.org/wiki/Fourier_Transform#Analysis_of_differential_equations", which is quite useful for solving some differential equations.

Last edited by a moderator: May 4, 2017