jeuclid-mathviewer: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/jeuclid-mathviewer - from package: jeuclid-mathviewer

You may install the required package with command apt-get install {package}

Error in other languages:
jeuclid-mathviewer: bevel nie gevind nie
jeuclid-mathviewer: comandă negăsită
jeuclid-mathviewer: comando não encontrado
jeuclid-mathviewer: commande introuvable
jeuclid-mathviewer: command not found
jeuclid-mathviewer: käsku ei ole
jeuclid-mathviewer: không tìm thấy lệnh
jeuclid-mathviewer: komanda nerasta
jeuclid-mathviewer: Kommando nicht gefunden.
jeuclid-mathviewer: kommandot finns inte
jeuclid-mathviewer: komut yok
jeuclid-mathviewer: nie znaleziono polecenia
jeuclid-mathviewer: níor aimsíodh an t-ordú
jeuclid-mathviewer: no se encontró la orden
jeuclid-mathviewer: no s'ha trobat l'ordre
jeuclid-mathviewer: opdracht niet gevonden
jeuclid-mathviewer: parancs nem található
jeuclid-mathviewer: perintah tidak ditemukan
jeuclid-mathviewer: príkaz nenájdený
jeuclid-mathviewer: příkaz nenalezen
jeuclid-mathviewer: команда не найдена
jeuclid-mathviewer: командата не е открита
jeuclid-mathviewer: 命令找不到
jeuclid-mathviewer: コマンドが見つかりません