Proff of the Numerical Derivative

[Jimmy84]

Homework Statement

Proff that f´(x) = the lim of delta x approaching to 0 of

f (a + delta x) - f (a -delta x) / 2 delta x

Homework Equations

The Attempt at a Solution

the book hinted me that I should solve it in this way


f (a + delta x) - f (a) + f (a) - f (a - delta x) / 2 delta x

but I am stuck here and I don't know how to proff this. I d appreciate some help, thanks a lot in advance.

 

[D H]

The word is prove, not proff.

Anyhow, try it with

$$\frac 1 2 \,\frac {f(a+\Delta x) - f(a) \,\,\,+\,\,\, f(a) - f(a-\Delta x)}{\Delta x}$$