Let <math>A, B \ </math> be sets. We say there is a '''rigid body equivalence''' <math>A \cong B \ </math> if <math>A \ </math> can be partitioned into finitely many sets <math>A_1, ..., A_n \ </math> and there are <math>n \ </math> rigid motions <math>g_1, ..., g_n \ </math> such that <math>g_1(A_1) \cup ... \cup g_n(A_n) = B \ </math>. | Let <math>A, B \ </math> be sets. We say there is a '''rigid body equivalence''' <math>A \cong B \ </math> if <math>A \ </math> can be partitioned into finitely many sets <math>A_1, ..., A_n \ </math> and there are <math>n \ </math> rigid motions <math>g_1, ..., g_n \ </math> such that <math>g_1(A_1) \cup ... \cup g_n(A_n) = B \ </math>. |