UPSKILL MATH PLUS

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Line
A line is obtained by extending the line segment infinitely in both directions. It has an infinite number of points. A line is labelled sort of a line segment with a bidirectional arrow over the label.
Line2.png
 
The above figure shows a line AB and is represented as \overleftrightarrow {AB} or \overleftrightarrow {BA}. Sometimes the line is denoted by a letter like m, as showed in the above line.
Example:
The 100 metres track is to illustrate the concept of the line. A track may be a line that extends infinitely in both directions without having a fixed starting and ending point.
run.png
Ray
A ray is a part of a line. It starts at one point and extends infinitely in the opposite direction. The ray has an infinite number of points.
The starting point that's fixed at one end is termed as a vertex of a ray.
 
Ray.png
 
The above figure shows a ray AB and is represented as \overrightarrow{AB}.
 
Important!
A ray name should start with a vertex and end in another direction.
 
The name of the above ray is \overrightarrow{AB} not \overrightarrow{BA}.
Example:
We have a battery-operated torch on one end of the road and, light from the torch (called as line segment) is travelling in a straight line towards the other direction. Since we don't know the end of that light, we will say that this line segment from a fixed source is a ray.
 
torch.png