The reducible 3-dimensional finite reflective group is dihedral symmetry, [ p,2], order 4 p, . The reflection generators are matrices R 0, R 1, R 2. R 0 =R 1 =R 2 =(R 0 ×R 1) =(R 1 ×R 2) =(R 0 ×R 2) =Identity. [ p,2] () is generated by 2 of 3 rotations: S 0,1, S 1,2, and S 0,2. An order p rotoreflection is generated by V 0,1,2, the product of all 3 reflections.