Derivations - What's Acceptable?

[BOAS]

Homework Statement

Hello,

this isn't really a h/w problem that fits the template, but here seems the most sensible place to post.

I am writing a paper (not original research) and part of the requirements is that I include a "comprehensive discussion of the relevant theory (including derivations of equations)". The experiment I will be writing about makes use of the lens makers formula. I know how to derive this but the derivation makes use of the equation $\frac{n_{1}}{p} + \frac{n_{2}}{q} = \frac{n_{2} - n_{1}}{R}$.

This equation in turn relies upon snell's law, which I can derive from fermat's principle.

My question is this;

If the experiment doesn't make use of the other equations, is it necessary to show their derivations, or is it acceptable to merely reference them?

I don't want to make it sound like I'm hoping you'll say 'just reference them' - I would actually like to show my lab instructor that I can derive it from first principles but I am worried that it might be viewed as unnecessary/an attempt to boost the word count etc.

What do you think?

 

[dauto]

I would start from Snell's law and use it to show all other relevant equations.