latex tabular

\begin{tabular} 
\vline
iii
\vline
\end{tabular}

Latex Tabellen werden anders gebaut (\vline funktioniert hier nicht).

\begin{array}{|rc|l}
a & b & c \\ \hline
d & e & f \\
g & h & i \\ \hline
\end{array}

Siehe: Mathematische Tabellen, Matrizen und Vektoren.

the best is a table created from spreadsheet

Wie bekomme ich, bitte, den Mittelstrich dazu?

\begin{array}{|c|c|}
\begin{array}
\text{Auch Symmetralen der Außen\angle aller \triangle}\\
\text{mit Seitenlängen }c = a_{o}+b{o},\;
\\
 a = k \cdot a_{o},\; b = k \cdot b_{o}
\text{. überraschen}
\end{array}
\begin{array}
\text{
Erstmal find uns aber} \\
\text{
die Formel für die Länge }
\\
\text{der Strecke } d
\end{array}
\end{array}

Type each line in cells like latex text

then select the cells, right click, create table. Then double-click in the table and edit the second parameter to "c|l|"

in tabletext() help you can see many another methods and example by Mike https://www.geogebra.org/m/Eq5T3vV3

you can change the colour in the menu bar above spreadsheet

also you can add ie: "\bold"A1 instead A1 in my text

Tankyou for your ama zing work that is bewildering me - I had not woked with ggb spreadsheet until now

and tried latex tabular only af ter I failded to get the desired resdult with arrays - but now managed with much eyestrain fighting typos . I hope to find time to study . your worlk after finishing the piece working am on now.