Origami Design Secrets 里的问题

5rj

原文：Origami Design Secrets 2ed_Robert J. Lang P306-307

The diagonal pattern is not a stable pattern; that is,
we could allow two pairs of faps to become somewhat larger   
without shrinking anything else. The two faps that can grow
are the two in the upper right corner of Figure 9.15. Can you
see why?

其中的 two pairs of faps指的是哪两对折翼呢？我看来看去都只有一对啊