Lesson 1 Objectives:

1. Understanding the undefined terms: point, line, plane.

2. Understanding the defined terms: collinear, coplanar, and intersection.

2. Drawing representations of points, lines and planes.

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The simplest figure in geometry is referred to as a **point**. It does not have a certain size and is often represent with a dot and labeled using capitol letters. Points are in all geometric figures and we define space to be the set of all points. Below are the points A and B.

Another familiar geometric figure is a **line**. A line extends in two different directions with no end. A line itself does not have any thickness and is labeled using a lower case letter. If you know that two points are on the line you can also define it using those two points. Below is line l or .

A geometric **plane** is suggested by a floor or wall. It extends with no end or edges and has no thickness, but when we draw a plane we normally draw it as a four-sided figure. Normally planes are labeled with capitol letters, just like points. Below is plane M:

**Collinear points** are points all in one line and **non collinear** points are points that are not on one line. Below points A, F and B are collinear and points G and H are non collinear.

**Coplanar points **are points all in one plane and **non coplanar points** are points that are not in the same plane. Below points B, C and E are coplanar, points D and A are coplanar but points E and D would not be coplanar.

The **intersection** of two figures is the set of all points that are in both figures. (The dashes in the diagrams indicate parts hidden from view in figures in space). Below are a few examples of intersections.

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__Student Exercises: __

Given the following figures classify each statement as true or false.