15. In figure 1-6, three points are labeled a, b, and c, and two borders are
labeled d and e. It is correct to say that a is
to b and c, b is
to a
and
to c, and c is
to a and b. We speak of d as the
border. We
speak of e as the
border.
Figure 1-6. Directions (exercise 15).
MD0006
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