In the figure above, ray AB, written symbolically as AB, contains all of the points on line AB from A in the directions of B.
The following are some examples of rays:
1. A laser pointer creates a ray of light.
2. The number line showing whole numbers is really not a line, but a ray. It begins at the endpoint, 0, and extends infinitely through 1 because there is no greatest whole number.
3. In coordinate geometry, an inequality can be represented as a ray on a number line.
The inequality x≥-1 can be represented by the ray above, whose endpoint is at -1 on the real number line.
A ray has a directional component so be careful how you name it. Ray AB is not the same as ray BA.
A ray with 3 labeled points can be named in different ways, as shown below. Just make sure to include the endpoint.
Angles and rays
An angle is formed when two rays share a common endpoint.
Did you know?
A ray of sunshine begins at the sun (the endpoint) and travels through space in one direction. A ray from the sun can be used as a model for thinking about a ray in geometry.