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. Created by Sal Khan and Monterey Institute for Technology and Education. To identify a ray in a picture, look for a line that has one endpoint (the point where the ray starts) and an arrow on the other end (to show that it keeps going). 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 ray is a shape that starts at one point and extends forever in one direction. A point represents position only it has zero size (that is, zero length, zero width, and zero height). A ray is a line that has a starting point and then goes on in a. It is represented by a dot and named by a capital letter. A line is straight and has two arrowheads which show that it continues in both directions.

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.

Slopes: Parallel and Perpendicular Lines.

Similar Triangles: Perimeters and Areas.

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.Lines: Intersecting, Perpendicular, Parallel.

Ray in real life geometry