Basic plane figures
● Point
>>> Point. A Point is a mathematical object, not a material one. But many material objects suggest what we think of as a point. A corner of this page, the tip of pencil, or a dot on a sheet of paper. (Many). For example, here we picture two points, labeled A and B. The ruler and protactor are important instruments used in drawing geometric figures.
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● line sigment
>>> Line segment or segment is another mathematical object, it is a set of points. It is suggested, for example, by an edge of a box. To picture the segment AB, we align a ruler with points A and B and draw a mark from A to B.
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We use a ruler also to measure line segments. Thus, the length of the segment pictured at the right is 1 1/2 inches. In Symbols, we write d(AB) = 1 1/2 in.
- The line AB includes segment AB but extends indefinitely in both directions. The ray AB includes segment AB and extends indefinitely beyond B, it includes the endpoint A. The half-line AB does not include the endpoint A.
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-CarryOnLearning-
