Geometry/Chapter 1/Lesson 1

In geometry, the words, point, line, and plane are undefined terms. These words do not have formal definition, but there is agreement about what they mean.

Collinear points are points that lie on the same line. Coplanar points are points that lie in the same plane.

Example 1 Name points, lines, and planes
 {Give two other names for line PQ and for plane R. PQ={ QP (i) _2 },{ n (i) _1 } R={ SVT (i) _3 },{ PTV (i) _3 }
 * type="{}" coef="4"}

{Name three points that are collinear. { S (i) _1 },{ P (i) _1 },{ T (i) _1 }
 * type="{}" coef="3"}

{Name four points that are coplanar. { S (i) _1 },{ P (i) _1 },{ T (i) _1 },{ V (i) _1 } DEFINED TERMS In geometry terms that can be described using known words such as point or line are called defined terms.
 * type="{}" coef="4"}