# How to combine two functions

1. Dec 8, 2013

### 1Keenan

hi all!

I have a problem related with some data analysis.
I have two functions, expressin the energy resolution of a certain device, and the are function of two differente variables. What I want to do is two write a function of two variables from the one variable function I have.

To be more clear, in my device I can write energy as:

E = A/x^2 an E=B/y where A is a contant that takes in account the geometry of the system and the magnetic field while be is a contant that takes in account the geometry of the system and the electric field (the system is a Thomson Parabola, but is not important)

I can write energy resolution as the derivativ of the previous function times a certain space interval:

DE = 2 (E)^(2/3) Dx / sqrt(A) and DE = E^2 Dy/B

This two derivatives are my resolution function respect to x and y, but they actually depend on E (th energy) not on the space.

How to write a function R(x,y) from the two previuos functions which gives me something like "isoresolution" curves?