# Inverse of erf(z)?

1. Feb 11, 2009

### DyslexicHobo

I'm taking a materials science class and we were introduced to the erf(z) function.

$$erf(z) = 2/sqrt(\pi) \int^{z}_0 {e^{-y^2}$$

Because the calculus required to calculate this is very lengthy, he pointed us to a table to look up the values. Instead, I programmed the function into my calculator to quickly find values for erf(z).

However, sometimes we need to find the value for z for a given value of erf(z). I'm having trouble solving explicitly for z, but it seems like there should be a good way to find the inverse of the function. I did some searching on Wikipedia, but I didn't understand the taylor series representation of the inverse; it included $$C_m$$ and $$C_k$$. I wasn't sure what to do with these. Can someone please explain it or tell me how to program an inverse of this function into my calculator?

Thanks.

The article I was reading can be found http://en.wikipedia.org/wiki/Error_function" [Broken].

Last edited by a moderator: May 4, 2017