1.1 Basics of Geometry
Points, Lines, and Planes
Pacing:This lesson should take approximately three class periods.
Goal:This lesson introduces students to the basic principles of geometry. Students will become familiar with three
primary undefined geometric terms and how these terms are used to define other geometric vocabulary. Finally,
students are introduced to the concept of dimensions.
Study Skills Tips! Start your students off on the correct foot – vocabulary is a necessity in geometry success!
Devote five minutes of each class period to creating flash cards of the major terminology of this text. Use personal
whiteboards to perform quick vocabulary checks. Or, better yet, visit Discovery School’s puzzle maker and make
your own word searches and crosswords (http://puzzlemaker.discoveryeducation.com/)!
Language Arts Connection!To give an example of why some words are undefined, use the concept of circularity.
Students use a dictionary, either electronic or paper (yes, they are still printed!) to complete this activity. Ask
students to look up the wordpointin their reference. Find a key word in that definition. Students should continue
this process until the wordpointis found. Repeat this process forlineandplane.The rationale behind this activity
is for students to see there is no one way to define these geometric terms, thus allowing them to be undefined but
recognizable.
Real World Connection!Have students identify real-life examples of points, lines, planes in the classroom, as well
as sets of collinear and coplanar. For example, points could be chairs, lines could be the intersection of the ceiling
and wall, and the floor is a great model of a plane. If your chairs are four-legged, this is a fantastic example of why
3 points determine a plane, not four. Four legged chairs tend to wobble, while 3−legged stools remain stable.
To help students understand dimension, use the following table:
TABLE1.1:
Zero-dimensional 1-dimensional (length) 2-dimensional (length and
width)3-dimensional (length,
width, and height)Have students write abstract examples of each dimension (point, line, plane, prism, etc) in the first row. Then have
students brainstorm real-life examples of each dimension. Complete the table by gathering the responses of various
students.
Segments and Distances
Pacing:This lesson should take one class period
Goal: Students should be familiar with using rulers to measure distances. This lesson incorporates geometric
postulates and properties to measurement, such as the Segment Addition Property.
Real World Connection!To review the concept of measurement, use a map of your community. Label several things
on your map important to students – high school, grocery store, movie theatre, etc. Have students practice finding
1.1. Basics of Geometry