Which undefined term is used to define an angle:
A) line
B) plane
C) point
D) ray
Answer – D) ray.
Ray is the postulate used to define the angle in geometry. The selection of this choice is essential in grasping the topic and the construction of angles. In geometry, certain fundamental aspects are held as being undefined for the simple reason that they cannot be explained in terms of other simpler conceptions. One of them is Ray, who is involved in angle description operation most significantly.
An angle is a figure made of two rays such that the two rays have the same initial point, which is called the vertex. They both are line segments and meet each other at the vertex forming the angle where each ray is a part of the angle. For example, let there be angle ABC. Point B is the vertex and BA and BC are two rays which are opposite to each other and together they bound the angle. Another reason behind the suitability of the ray specifically for angles is that it has a fixed starting point known as the vertex and it goes on to infinity in one direction to represent several measurements of an angle.
By employing the rays to identify or establish angles, the tutor is also in a position to introduce other concepts particularly angle bisectors and supplementary angles. An angle bisector for instance is a ray that passes through the middle of an angle and divides the same into two equal parts. Angle sums that equal 180 degrees can be understood by drawing a ray from a point on a straight line in two angles.
The application of rays when identifying angles is used in defining the major classes of angles including; acute angles, obtuse angles, right angles, and reflex angles. The definition also maintains uniformity when it comes to the study of other geometrical concepts and the proofs involving angles. With the help of a classic example where geometers continue to use the undefined term ‘ray’ as a definition of angles, they have built a firm ground for future mathematical construction.
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