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  • A point determines a location. The tip of a compass, the sharpened end of a pencil, the pointed end of a needle, etc., are the examples of points. Generally, points are denoted by capital letters.
  • A line segment corresponds to the shortest distance between two points. The line segment joining the points P and Q is denoted as .


  • A ray is a portion of a line, which starts at one point and goes endlessly in a direction.


This ray is denoted as . Arrow head is towards Q since it is extended along Q.

  • When a line segment PQ is extended indefinitely on both sides of points P and Q, it becomes a line, . Line is usually denoted by small letters l, m, n.


  • Two lines l and m are said to be intersecting lines, if they intersect at a point.


  • Two lines are said to be parallel lines, if they never intersect each other. We can represent the given lines as l||m.


  • A plane is a flat surface having length and width, but no thickness. We can say that a plane is a flat surface, which extends indefinitely in all directions. For example, surface of a wall, floor of a ground, etc.
  • Incidence properties in a plane:
    1. An unlimited number of lines can  be drawn passing through a given point. 
    2. There is exactly one line passing through two distinct points in a plane.
    3. Points lying on the same line are known as collinear points and the points which do not lie on the same line are called non-collinear points.
    4. Three or more lines passing through a common point are known as concurrent lines and that point is known as point of concurrence.


  • One complete turn of the hand of a clock is one revolution. The angle of one revolution is called a complete angle.

  • A right angle is of a revolution and a straight angle is  of a revolution.


  • 1 complete angle = 2 straight angles = 4 right angles
  • 1 straight angle = 2 right angles 
  • If an angle measures less than a right angle then it is know…

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