is defined as $r_M = (21\, \textrm{MeV}/\epsilon) l_0$, being the mean square scattering angle of electron with the critical energy $\epsilon$ $(\sim 82\, \textrm{MeV})$, along one radiation unit $l_0$. We define a function $f(\theta,\varphi, r/r_M, E;s)$ as follows: $$\Delta N(\theta,\varphi, r/r_M, E;s)=N(s)f(\theta,\varphi, r/r_M, E;s)\Delta \theta\Delta\varphi\Delta log\,(r/r_M) \Delta log E\;\textnormal{,}$$ where $N(s)$ is the total number of electrons at level $s$. Note that the function $f(\theta,\varphi, r/r_M, E;s)$ has been defined for a single shower. However, we will show that for large showers, i.e. such that the numbers $\Delta N$ are large ($>100$), *this function is universal*. This means that it is independent of the primary particle energy, its mass, the incidence angle or even of the fluctuations in the shower development (thus the requirement $\Delta N>100$). The function $f$ can be represented as a product of functions, each depending on one variable and some parameters, as follows: $$f(\theta,\varphi, r/r_M, E;s)=f_E(E;s)f_r(r/r_M;E,s)f_{\varphi}(\varphi;r/r_M,E,s)f_{\theta}(\theta;\varphi,r/r_M,E,s)     \;\textnormal{.}$$ The variables on the r.h.s. of the semicolons are the parameters of the functional dependence on the variables before the semicolons. The functions $f_E,f_r,f_{\varphi}$ and $f_{\theta}$ are normalized to unity when integrated over $log\,E$, $log\,(r/r_M)$, $\theta$ and $\varphi$ respectively. They are correspondingly the distributions : of electron energy $E$ 