Simply Explicitly Invertible Approximations to 4 Decimals of Error Function and Normal Cumulative Distribution Function

A. Soranzo, E. Epure

We improve the Modified Winitzki's Approximation of the error function $erf(x)\cong \sqrt{1-e^{-x^2\frac{\frac{4}{\pi }+0.147x^2}{1+0.147x^2}}}$ which has error $|\varepsilon (x)| < 1.2…