The word plane is written with the letter so as not to be confused with a point (Figure 4 ). Unit 1: Geometry Basics unit geometry basics (name) naming points, lines, and planes: practice use the diagram to the right to name the following. A single capital letter is used to denote a plane. It is usually represented in drawings by a four‐sided figure. A plane has infinite length, infinite width, and zero height (or thickness). In Figure 3 , points M, A, and N are collinear, and points T, I, and C are noncollinear.įigure 3 Three collinear points and three noncollinear points.Ī plane may be considered as an infinite set of points forming a connected flat surface extending infinitely far in all directions. If there is no line on which all of the points lie, then they are noncollinear points. Points that lie on the same line are called collinear points. Key Words undefined term point, line, plane postulate collinear, coplanar segment ray endpoint 1.3 Points, Lines, and Planes Postulate 1 Two Points Determine a Line Words Through any two points there is. A line may also be named by one small letter (Figure 2). plane C l B line A point undefined terms 14 Chapter 1 Basics of Geometry Goal Use postulates and undefined terms. The symbol ↔ written on top of two letters is used to denote that line. A line has infinite length, zero width, and zero height. It extends infinitely far in two opposite directions. Figure 1 illustrates point C, point M, and point Q.Ī line (straight line) can be thought of as a connected set of infinitely many points. A point represents position only it has zero size (that is, zero length, zero width, and zero height). It is represented by a dot and named by a capital letter. Although these terms are not formally defined, a brief intuitive discussion is needed.Ī point is the most fundamental object in geometry. These terms will be used in defining other terms. Because that meaning is accepted without definition, we refer to these words as undefined terms. Points Lines and Planes in Geometry is the lesson that many teachers skip or fly through because they assume (in huge air quotes) that the students know. This process must eventually terminate at some stage, the definition must use a word whose meaning is accepted as intuitively clear. When we define words, we ordinarily use simpler words, and these simpler words are in turn defined using yet simpler words. Point, line, and plane, together with set, are the undefined terms that provide the starting place for geometry. Summary of Coordinate Geometry Formulas.Slopes: Parallel and Perpendicular Lines.
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