Which is defined using the undefined terms point and line?

Which is defined using the undefined terms point and line?

A) angle

B) circle

C) parallel lines

D) ray

Answer: D) ray

A ray is described using two undefined terms point and line. Thus, it is considered to be among the most basic geometric notions. Mathematically, a ray is taken or considered from a line which is limitless in extent towards one and only one point. This definition entails the use of two entities, that is the point and the line, which geometers consider as primitive notions.

To understand this better, let’s break it down:

A point is a place in space which possesses no magnitude at all. Technically it is an employment or a post, it does not have any width, length or even depth. There is, however, a Line which is a straight line which is drawn zigzag and has no width and is extended indefinitely on either side. These two are regarded as non-defined as they are prime and generic concepts and therefore can’t be defined further.

With these undefined terms, we can define what a ray is. It goes on forever in one direction from a certain terminal point, which is termed the endpoint, and is situated on a line. For instance, the examples might be a laser pointer or any other similar device. The point the light comes out clearly defines the tip of the laser as the point while the ray can be described as the via sensor like a line of light going outwards. It points only in one direction which is infinitely far but has a definite origin at the junction of four beams.

Geometrically a ray is represented by an arrow placed over two letters, like AB→ where A is a fixed point and B is any other point of the ray. This notation works to stress the fact that, although the ray begins at point A, it extends beyond point B and goes on forever.

Building on the knowledge of rays, there are other more complex geometrical concepts; for example, the angle is made by two rays that have the same initial point.