Lines, line segments and half lines
Key Notes :
A line goes without end in both directions.
A ray has 1 endpoint and goes without end in 1 direction.
A line segment has 2 endpoints.
Understanding Lines, Line Segments, and Half Lines
I. Introduction
A. Definition of a Line
- A line is a straight, continuous path that extends infinitely in both directions.
- It is represented by a straight line with arrowheads on both ends.
B. Importance of Lines
- Lines are fundamental in geometry and have various applications in real-world scenarios.
- They are used to represent paths, boundaries, and relationships in mathematical and scientific contexts.
II. Line Segments
A. Definition
- A line segment is a part of a line with two endpoints.
- It has a finite length and can be measured in units.
B. Characteristics
- Unlike lines, line segments have a defined length.
- They are represented by a portion of a line between two distinct points.
C. Examples
- Illustrate examples of line segments in everyday situations.
- e.g., a piece of string, a segment of a road, etc.
III. Half Lines (Rays)
A. Definition
- A half line, also known as a ray, is a part of a line that has one endpoint and extends infinitely in one direction.
B. Characteristics
- Rays have no endpoint in the direction they extend.
- They are represented with an arrowhead on one end to indicate the direction of infinity.
C. Examples
- Relate rays to real-life scenarios.
- e.g., sunlight extending from the sun, a flashlight beam, etc.
IV. Key Concepts
A. Naming Lines and Segments
- Lines and line segments can be named using capital letters or by using symbols.
- e.g., Line AB or AB, where A and B are endpoints.
Learn with an example
1) What is this?
- line
- line segment
- ray
Now look at this figure:
This is a ray . It has 1 end point.
2) What is this?
- line
- line segment
- ray
Now look at this figure:
This is a line segment . It has 2 end points.
3) What is this?
- line
- line segment
- ray
Now look at this figure:
This is a line. It never ends.
let’s practice!
