SWBAT describe points, lines, planes, and space in terms of the number of their dimensions. Students will understand the difference between solid and plane figures.

Understanding precise definitions of geometric figures begins with the concept of dimension. This engaging re-telling of a classic tale gets us started.

5 minutes

Today's Warm Up** **asks students to explain the difference between "2-D" and "3-D". This gives me a chance to see what my students already know about the concept of dimension, and it gives them a chance to connect with prior knowledge. I find that many of my students know only a little: to some, "3-D" is a special enhancement to certain movies.

I display the prompt using the slideshow for the lesson. The lesson opener follows our Team Warm-up routine, with students writing their answers in their Learning Journals.

**Goal-Setting**

I display the Agenda and Learning Targets for today's lesson. I tell my students that "dimension" is a difficult word to define, so I will be giving them lots of examples to help them understand the concept. The movie we are about to see does a good job of introducing the main ideas. At the end of the lesson, they should be able to describe the difference between objects that are 3-dimensional and those which have only 2 dimensions.

4 minutes

We will end this lesson by following our Team Size-Up routine. The Lesson Close prompt asks students to compare the number of dimensions of Flatland to the number of dimensions in our own world. I will refer to Flatland throughout the unit to help students understand the concept of a plane.

**Homework**

For homework, I assign problems #9-11 from Homework Set 1. These problems ask students to apply definitions and concepts that we have not really discussed, but were introduced in the movie. Problem #9 asks students to classify familiar geometric objects according to number of dimensions. Problem #10 asks students to find examples of polygons in the real world. I emphasize that the polygons do not have to be regular. Many can be found among the block letters on road signs during their bus ride home. Problem #11 introduces the concept of a cross-section, which was explored in the movie.