Largely based on the representation of a translation or rotation as the
composition of two reflections, Chapter 7 thoroughly (and purely
compositions of isometries; although this investigation is often carried
out in the context of a wallpaper pattern, it should be possible to study
this chapter independently of the rest of the book. Section 7.0 offers a
more 'empirical' way of determining isometry composition, and is therefore
largely independent of the rest of the chapter.