Points, Lines, and Planes

Lesson Plan - Get It!

Audio:

Vocabulary Look up these definitions at Mathwords.com, and be sure to write them down and even memorize them!

• collinear
• coplanar
• line
• plane
• point
• postulate

Although you now have the definitions of the vocabulary words listed above, sometimes math terms are easier to understand when put into an explanation. The following is a discussion concerning how the vocabulary words above relate to each other and geometry:

A point can be thought of as a location. Consider your computer screen. If you place your finger on it, you have just identified a point. If you move your finger to another place on your computer screen, then you have located another point. You use a capital letter whenever labeling a point in geometry. Points are located everywhere!

A series of points is a line. A line extends in both directions indefinitely. You label a line by listing two of the points found on it. All points located on the same line are referred to as being collinear.

A plane is flat surface that extends in all directions. It is very important to note that a plane does not have any thickness. You label a plane simply with one capital letter, or by naming 3 non-collinear points on the plane.

Finally, all lines and points located on the same plane are referred to as coplanar.

A postulate is a statement in math that is accepted as true. It does not need to be proven. Below are 4 postulates and an example of each. You may recognize them from your algebra lessons.

• Postulate 1-1: Through any two points there is exactly one line.
• Postulate 1-2: If two lines intersect, then they intersect in exactly one point.
• Postulate 1-3: If two planes intersect, then they intersect in a line.
• Postulate 1-4: Through any three non-collinear points there is exactly one plane.

The next two sections of the lesson offer opportunities for you to expand your knowledge of the above geometric terms and postulates.