Geometry: Understanding Ray Lines

What is a Ray Line?

• A ray line, also called a ray, is a one-dimensional, straight figure that extends infinitely from a single endpoint, also called the point of origin.
• A ray has an endpoint at one end and an arrow indicating it continues indefinitely without ending at the other end.
• Real-life examples of rays include light from the sun and a flashlight, with the source being the endpoint.

Naming a Ray

• A ray can be named using its endpoint and one other point on the ray, such as "Ray AB".
• Alternatively, rays can be named simply with their endpoint, such as "Ray A".
• When using two letters to name a ray, always name the endpoint first and the other point second.

Measuring a Ray

• A ray line cannot be measured because its length is indefinite.
• Rays have a starting point (the endpoint), but they continue in the same direction forever, making measurement impossible.
• The length of a ray is infinite.

What is a Line Segment?

• A line segment is a one-dimensional, straight figure with two endpoints, a beginning, and an end.
• Line segments are named by their two endpoints (e.g., "line segment AB").
• Line segments are used in everyday life, such as in architecture, sports, and everyday objects.

Measuring a Line Segment

• A line segment can be measured from endpoint to endpoint.
• To measure a line segment, use a ruler, yardstick, or other measuring device to find the distance between its two endpoints.
• The length of a line segment is the distance between its two endpoints.

Difference Between a Line and a Line Segment

• A line is a one-dimensional, straight figure that extends infinitely in opposite directions.
• A line segment is a finite piece of a line with two endpoints.
• Lines cannot be measured, while line segments can be measured.

Difference Between a Line and a Ray

• A line extends infinitely in opposite directions, while a ray extends infinitely in one direction from its endpoint.
• A line has no endpoints, while a ray has a single endpoint.
• Neither lines nor rays can be measured because their lengths are infinite.

Adding Line Segments

• To add line segments, measure each segment separately and add the measurements to find the total length.
• Alternatively, line segments can be lined up end-to-end and measured from the first endpoint to the last endpoint to find the total length.

Learn about ray lines, also known as rays, and how they are defined in geometry. Discover how to name a ray and explore real-life examples.