上海大孝 SHIANCH AI JLAO IONG LNTVERSTY 9.1 Preliminaries A: A set in Z2 with elements of a=(a,, a2) B∈{ww=-b,forb∈B, Reflection (A)∈{c=a+,fra∈A}, Translation9.1 Preliminaries • A: A set in Z2 with elements of a = (a1 , a2 )