#### 4.1.1 General syntax

• The general syntax of a TEXgraph command is : [argument1, ..., argumentN], in case there is only one argument, hooks are optional (the hooks represent the function Liste). Each argument is a mathematical expression.
• Running the command consist in evaluating each argument and returning the results’s list that differ from Nil.
• Exemple(s)
• [2,1+i,sqrt(-2),"toto",1/2] returns the list: [2,1+i,"toto",0.5].
• Seq(k^2,k,1,5) returns the list: [1,4,9,16,25].
• Droite(0,1+i) returns the value Nil, but the function Droite has a graphical effect if used in a graphical user element.
• Consider three global variables: $A$, $B$ and $C$. Then the command [C,C+i*(B-A)] returns $C$’s value followed by the value $C+i\left(B-A\right)$. That expression can be used to define the perpendicular to $\left(AB\right)$ passing through $C$.
• Supose we have to build a triangle $\left(ABC\right)$ with its three medians as a single graphical element, then :
• we choose Graphical elements/Create/User,
• we give a name to the objet,
• we enter the command:
[Ligne([A,B,C],1), Droite(A,(B+C)/2), Droite(B,(A+C)/2), Droite(C,(A+B)/2)]
The functions Ligne and Droite return the Nil value and has a graphical effect in the user context.
• There are still three variables to create: $A$, $B$, $C$ (if not already done). Of course, the polyline and the three straight lines can be separately created.
• Calculations on the positive numbers are theorytically in the interval $\left[1{0}^{-324},1{0}^{308}\right]$.
• TeXgraph is case sensitive.
• Each TeXgraph object is identified by an identifier (or name), that has to follow the rules:
• Beginning with a letter.
• Less than $35$ caracters.
• A caracter has to be among: a letter, a figure, a quote, or an underscore.