## Length

60 minutes; extension (optional) 30 minutes

## Curriculum Standards

- CCSS.Math.Content.HSG.CO.A.1

Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.

- CCSS.Math.Content.HSG.CO.A.2

Represent transformations in the plane using, e.g., transparencies and geometry software; describe transformations as functions that take points in the plane as inputs and give other points as outputs. Compare transformations that preserve distance and angle to those that do not (e.g., translation versus horizontal stretch).

## Materials

## Instructions

- Begin the lesson by asking students to discuss one concept they know about geometry.
- Then explain that this lesson explores four undefined geometry terms.
- Distribute the Undefined Terms of Geometry: Concepts & Significance lesson, play the video, pause at 1:50, then start the following discussion:
- What are undefined terms of geometry?
- Define a point and discuss their purpose.

- Now restart the video, pause at 3:57, then pose the following:
- How does the author define a line?
- How are lines labeled?
- What are planes?

- Next play the video until the end, then ask students to explain a set and how they are written.
- Afterwards, show the lesson quiz, pair students and ask them to answer each question.
- Then review for accuracy.

## Activity

- Begin by asking students what they learned from the lesson.
- Now tell them they are going explore the undefined terms further.
- Lay the butcher paper on the floor, divide the class into four groups and assign one of the following to each:
- Now explain these instructions:
- Peruse the hard copy lesson and identify the characteristics of your assigned undefined term
- Use one foot of the butcher paper to list the characteristics and draw an example

- Afterward, tape the completed butcher paper to the board.
- Then ask each group to explain their undefined term; require all students to participate.

## Extension

- Begin by telling students they are going to play a game.
- Pair students and distribute a piece of paper and pen/pencil to each.
- Explain that they will have 30 seconds to identify an undefined term around the classroom.
- Start the timer and ask students to identify and write down examples of planes.
- Now ask pairs to share their answers; walk around to ensure students do not add another pairs' identification to their paper.
- Note who received the most accurate answers.
- Now complete the steps above until the point, line, and set are identified.
- Give a small prize to the pairs who identified the most undefined terms.