18. If we mark a third dot, “C,” on our paper and wish to define its
position, we may give the direction and the distance from “A,” or from
“B,” or, if we prefer, we may follow the principle of Triangulation and
give two directions, one from “A” and the other from “B.” No distances
need be given in that case. The position of “C” will be found at the
intersection of the two directions.
[Illustration: Fig. 6]
The principle of Triangulation is illustrated in the above diagram.