CHAPTER 1 : BASIC CONCEPTS IN GEOMETRY
1.1 Points, Lines & Planes
The most fundamental geometric form is a point. It is represented as a dot with a capital alphabet which is its name (Figure 1.1) A line is a set of points and it extends in opposite directions up to infinity. It is represented by two points on the line and a double headed arrow or a single alphabet in the lower case (Figure 1.1) A plane is a two dimensional (flat) surface that extends in all directions up to infinity.
A plane has obviously no size and definitely no shape. However it is represented as a quadrangle and a single capital letter (Figure 1.1)
Figure 1.1 shows points A, D & Q, line AB, line l and plane P.
Some axioms regarding points, lines and planes are given below.
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An infinite number of lines can be drawn through any given point.
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One and only one line can be drawn through two distinct points.
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When two lines intersect they do so at only one point.
Collinear And Coplanar
Three or more points are said to be collinear if a single line contains all of them. Otherwise they are said to be non collinear. (Figure 1.2)
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