# Fourier Series (Clarification of Concept)

1. Oct 16, 2014

### galaxy_twirl

Hi everyone. I ran into a problem while attempting my Fourier Series tutorial. I don't really understand the "L" in the general formula for a Fourier Series (integration form). I shall post my question and doubts as images. Thank you for any assistance rendered.

<I am solving Q3 in the image.>

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2. Oct 16, 2014

### Simon Bridge

3. Oct 16, 2014

### galaxy_twirl

Hi Simon. Thank you for your reply. The limits of the integral sign denotes which part of a graph you want to integrate. However, I am confused by the L outside the integral. From what I observe, it seems that L (outside the integral sign) is different from [-L, L] (which is your domain over which you want to integrate). Am I right to say this?

Thank you.

4. Oct 16, 2014

### LCKurtz

They are the same $L$. By the way, posting images instead of typing your work is frowned on in these forums. That goes double for images that are posted sideways.

5. Oct 16, 2014

### Simon Bridge

The same rules apply to that L as for any letter used as a name for a constant or a variable in algebra.
That L is just a number. Where you see it, it's the same number.

6. Oct 17, 2014

### epenguin

But if you do do that, there are apps, at least one I know called DocScan HD which if you are taking these with I-pad or similar cleans them up from the hard-to-read grey-yellow.

7. Oct 20, 2014

### galaxy_twirl

8. Oct 20, 2014

### galaxy_twirl

I see. Thank you. I think I know where my mistake was. I failed to see that f(x) was 0 over a certain range, so I could have just changed the limits to (-pi/2) to (pi/2). :)

9. Oct 20, 2014

### galaxy_twirl

Hi epenguin. Thank you for your suggestion. The reason why I posted my question as a picture was because I am not familiar with LaTeX and I found that it can be quite hard to read if I typed it in purely character form. I will take note of your suggestion and try to type my questions out in the future. Thanks again.