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**[SOLVED] Evaluating electric field**

## Homework Statement

I have an electric field in the z-direction given by: (where sigma is charge per area and z is a distance)

[tex]

{\bf{E}} = \frac{{\sigma z}}{{2\pi \varepsilon _0 }}\left( {\frac{1}{z} - \frac{1}{{\sqrt {R^2 + z^2 } }}} \right){\bf{z}}

[/tex]

I have to evaluate this for z >> R.

## The Attempt at a Solution

Do I just insert R=0 or what? I overheard someone talk about Taylor-expanding it, but I don't see how/why?