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# What are three undefined terms in geometry?

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Three undefined terms in geometry are point, line and plane. These three terms are explained but not defined as everyone has an intuitive idea of these concepts. These terms serve as the foundation on which geometry is built.

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Space is the biggest set in geometry. All other sets are subsets of space. Points, lines, planes, angles and rays are all subsets of space. A point is dimensionless and hence cannot be physically represented on paper. However, for the purpose of the study of geometry it is represented by a dot on paper.

A line does not have width, and it is infinite in length. Again, this makes it impossible to represent an entire line on paper. A plane has no thickness and no boundaries. It stretches indefinitely in all directions. It is represented on paper as a four sided closed figure.

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## Related Questions

• A:

In geometry, a plane is defined as a flat, infinite surface. It has infinite length and width but no thickness. A plane is thus a two-dimensional, boundless surface and a subset of space.

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• A:

In geometry, a vertex is defined as a point where two or more lines meet. A triangle has three vertices. A parallelogram has four vertices. A six-sided figure has six vertices. A pentagon is a five-sided figure and has five vertices.

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In geometry, the intersection of two planes forms a line. This is one of the basic postulates put forth by Euclid in his geometry treatise of 13 books called "Elements". Postulates in geometry are basic assumptions that are generally accepted without requiring proof.