Restklassenringe (Z)/mod 9/Additionstafel

${\begin{array}{c||c|c|c|c|c|c|c|c|c|}+&0&1&2&3&4&5&6&7&8\\\hline 0&0&1&2&3&4&5&6&7&8\\1&1&2&3&4&5&6&7&8&0\\2&2&3&4&5&6&7&8&0&1\\3&3&4&5&6&7&8&0&1&2\\4&4&5&6&7&8&0&1&2&3\\5&5&6&7&8&0&1&2&3&4\\6&6&7&8&0&1&2&3&4&5\\7&7&8&0&1&2&3&4&5&6\\8&8&0&1&2&3&4&5&6&7\\\end{array}}$