![]() ![]() When making geometric drawings, be sure to be clear and label all points and lines. Postulate 5: If two distinct planes intersect, the intersection will be a line. Postulate 4: If two distinct lines intersect, the intersection will be one point. The word plane is written with the letter so as not to be confused with a point (Figure 4 ). Postulate 3: If a line and a plane share two points, then the entire line lies within the plane. 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. A line may also be named by one small letter (Figure 2). 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. ![]() 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.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. Slopes: Parallel and Perpendicular Lines plane C l B line A point undefined terms 14 Chapter 1 Basics of Geometry Goal Use postulates and undefined terms.A basic undefined term of geometry extends indefinitely in both directions and has no. Similar Triangles: Perimeters and Areas This is the most basic building block of geometry.Proportional Parts of Similar Triangles.Formulas: Perimeter, Circumference, Area.Proving that Figures Are Parallelograms.Triangle Inequalities: Sides and Angles.Special Features of Isosceles Triangles.Classifying Triangles by Sides or Angles 3 or more non-collinear points that lie in the same plane.Lines: Intersecting, Perpendicular, Parallel. ![]()
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