The Ruler and Dividers

Abstract

A ruler is used to draw lines. A dividers is used to carry distances. Both are everyday tools used by a drafter. If you have seen what looked like a compass with two points and no place for a pencil, that was a dividers. As a compass is sometimes called a pair of compasses, a dividers is often called a pair of dividers. Given points A,B,C,D with A ≠ B, the dividers is used to construct the point P on $\overrightarrow {AB}$ such that AP = CD. Therefore, with the dividers we can copy segments. Can we swing the dividers with one end on a point until the other end comes to rest on a given line? No, only because it is against the rules here; we call the tooi that does that a compass. Knowing the allowed use of the dividers, you should expect the definition below. For practice in formulating these definitions, you should write down the definition of a ruler and dividers point before you read any further.