What do the subscripts fpq and fqp mean in coupled oscillators and waves?

[roam]

Homework Statement

The following is a question from an old assignment on coupled oscillators and waves:

http://img214.imageshack.us/img214/601/question2.jpg

The Attempt at a Solution

So, I'm a confused about the meaning of the subscripts f_pq and f_qp. What do they mean?

Do f_p and f_q refer to partial derivatives of the function? If so what do f_pq and f_qp mean?

I've consulted the textbook physics of vibrations and waves, but I couldn't see what these subscripts stand for. Any help or suggestion would be greatly appreciated.

 

[SOA Andrew]

The symbol $f_p$ represents the partial derivative of $f$ with respect to $p$ (and similarly for $q$) while the symbol $f_{pq}$ may be better understood when rewritten as $(f_p)_q$. In words, differentiate $f$ with respect to $p$ and then differentiate the resulting derivative with respect to $q$.

 

[roam]

The symbol $f_p$ represents the partial derivative of $f$ with respect to $p$ (and similarly for $q$) while the symbol $f_{pq}$ may be better understood when rewritten as $(f_p)_q$. In words, differentiate $f$ with respect to $p$ and then differentiate the resulting derivative with respect to $q$.

Thank you so much for the clarification. I see, the notation they've used wasn't clear.