\newcommand

luca34″ post=117055Hi, in order to help you you should explain better what the command you want to do.
For example if you want the command /num overlines the argument of the command you’re wrong in the syntax, the correct one is the following:

`\newcommand{\num}[1]{\overline{1}} `

Ti ringrazio per la risposta veloce però non ha funzionato. Ho ottenuto questa risposta
! Missing = inserted for \ifnum.

D
l.19 \newcommand
{\num}[1]{\overline{1}}
premetto che \newcommand{num}{\overline{\nu}}
ha sempre funzionato e che se premo r quando il compilatore si arresta al primo \newcommand tutti i comandi \newcommand vengono presi , come per esempio
\newcommand{\Dr}{\frac{d}{d r}}. Quindi forse posso tralasciare

Adesso ti spedisco l’inizio del file latex con cui lavoro.
\documentclass[12pt]{article}
\DeclareMathSizes{12}{15}{8}{10}
\usepackage{graphicx}
\usepackage[T1]{fontenc} % Dysplay “<" and ">” symbols correctely
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathptmx}
\usepackage{placeins}
\usepackage{caption}
\usepackage{biblatex}
%\usepackage{xkeyval}
%\makeatletter
%\renewcommand{\theequation}{\thesection.\arabic{equation}}
%\newtheorem{theorem}{Theorem}
%\newtheorem{lemma}{Lemma}
%\newtheorem{corollary}{Corollary}
%\newtheorem{remark}{Remark}
%\newtheorem{proposition}{Proposition}
\newcommand{\num}[1]{\overline{1}}
%\newcommand{\num}{\overline\nu_m}
\newcommand{\muion}{\mu_{ion}}
\newcommand{\sigmai}{\sigma_{ion}}
\newcommand{\sigmaiN}{\sigma_{iN}}
\newcommand{\muei}{\mu_{ei}}
\newcommand{\muie}{\mu_{ie}}
\newcommand{\muiN}{\mu_{iN}}
\newcommand{\mueN}{\mu_{eN}}
\newcommand{\viz}{V_{iz}}
\newcommand{\vez}{V_{ez}}
\newcommand{\vte}{V_{T_e}}
\newcommand{\vgas}{V_{gas}}
\newcommand{\bion}{b_{ion}}
\newcommand{\biN}{b_{iN}}
\newcommand{\beN}{b_{eN}}
\newcommand{\etarr}{\eta_{rr}}
\newcommand{\etartheta}{\eta_{r \theta}}
\newcommand{\etathetar}{\eta_{\theta r}}
\newcommand{\etathetatheta}{\eta_{\theta \theta}}
\newcommand{\etazz}{\eta_{zz}}
\newcommand{\pa}{\partial}
\newcommand{\vx}{\overline{V_x}}
\newcommand{\Dz}{\frac{d}{d z}}
\newcommand{\Pz}{\frac{\pa^2}{\pa z^2}}
\newcommand{\rr}{\frac{\pa^2}{\pa r^2}}
\newcommand{\Px}{\frac{\pa^2}{\pa x^2}}
\newcommand{\pz}{\frac{\pa}{\pa z}}
\newcommand{\Dr}{\frac{d}{d r}}
\newcommand{\pr}{\frac{\pa}{\pa r}}
\newcommand{\Dx}{\frac{d}{d x}}
\newcommand{\dz}{\frac{d^2}{d z^2}}
\newcommand{\dr}{\frac{d^2}{d r^2}}
\newcommand{\dx}{\frac{d^2}{d x^2}}
\newcommand{\an}{\psi_{1n}}
\newcommand{\bn}{\psi_{2n}}
\newcommand{\dtheta}{\frac{d}{d \theta}}
\newcommand{\nuion}{\nu_{\text{ion}}}
\newcommand{\Viz}{V_{iz}}
\newcommand{\Vir}{V_{ir}}

\title{On the solutions of Grad-Shafranov equation for the protosphera}

\author{ Paolo Buratti$^{1}$,Brunello Tirozzi$^{1,2}$, Franco Alladio$^1$, Paolo Micozzi$^1$\\
$^1$ Enea Research Center, Frascati, Italy\\ $^2$ Department of Physics, University La Sapienza of Rome, Italy}

\begin{document}

\maketitle

Let us start from the Grad-Shafranov equation

\begin{equation}
\Pz\psi+r \pr (\frac{1}{r}\pr \psi)=-r j_\phi
\end{equation}

where

$$j_\phi= r \frac{d p}{d \psi}+\frac{I_A(\psi) I_(\psi)^{‘}}{r}$$

where $I_A$ is an arbitrary flux function which takes the value $1$ outside the plasma region, \cite{Nucl.Fusion}, $p$ is the plasma pressure.

$$ I_A(\psi) I_A(\psi)^{‘}=K \psi \rightarrow I_A= K^2 \psi$$

The magnetic field is represented

E’ chiaramente un testo matematico e \Pz è stato accettato come risulta dal pdf ( guarda le prime righe. \Pz è stato definito come derivata seconda rispetto a z nel newcommand relativo. Il problema è sapere perchè debbo premere r per fargli prendere il \newcommand. Ti allego anche il file latex. Quando compili ti dà errore perchè non ti allego le figure. Non serve per questa discussione