Geometry

• 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…