We now have 64 symmetries in R C, and 64 more symmetries of the form
with 2 R C. In the second category are the rotations by 90 and 270, as
well as the reflections across the diagonal axes. Together, these symmetries form a
group H of order 128. Since does not commute with all elements of R C, we
know that H is not the direct product of R C and Z = Instead, H is a
semi-direct product [9] of these groups: