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CHAPTER 6 TWO-COLORED WALLPAPER PATTERNS 6.0 ...

CHAPTER 6 TWO-COLORED WALLPAPER PATTERNS 6.0 ...

CHAPTER 6 TWO-COLORED WALLPAPER PATTERNS 6.0 ...

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described in this section. Indeed if we view a cm two-colored<br />

pattern as a ‘merge’ of a pm pattern (reflections) and a pg pattern<br />

(glide reflections), we see that there are only two possibilities for<br />

each ‘partner’: only pm, pm′ for pm (6.4.4 rules out p b<br />

′ 1m and c′ m ,<br />

while 6.4.3 rules out p′m and p b<br />

′ g ) and only pg, pg′ for pg (p b<br />

′ 1g is<br />

ruled out by 6.4.4). But two × two = four, and we can certainly write<br />

down the new (cm) types as ‘products’ of the old ones (pm, pg):<br />

cm = pm × pg, cm′ = pm′ × pg′ , p c<br />

′ g = pm′ × pg, p c<br />

′ m = pm × pg′<br />

Of course this ‘multiplication’ was first introduced in section<br />

5.7, where we viewed pmm2s as ‘products’ of pm11s and p1m1s.<br />

6.4.6 Further examples and symmetry plans.<br />

Fig. 6.37<br />

cm′ p c<br />

′ g p c<br />

′ m<br />

cm<br />

cm′

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