Unit 1, Lesson 7
No Bending or Stretching
Grade 8
Preparation
Lesson Narrative
In this lesson, students compare the side lengths and angle measures of a figure and its image under a translation, rotation, or reflection. They observe that the corresponding sides are the same length and the corresponding angles have the same measure, and learn that a transformation with this property is called a rigid transformation. In order to observe this property, students create a measuring tool using available materials (MP5). Then, students identify which figure is the image of an original under a rigid transformation and make arguments to explain their reasoning (MP3).
- Comprehend the phrase “rigid transformation” to refer to a transformation where all pairs of corresponding distances and corresponding angle measures in the figure and its image are the same.
- Draw and label a diagram of the image of a polygon under a rigid transformation, including calculating side lengths and angle measures.
- Identify (orally and in writing) a rigid transformation using a drawing of a figure and its image.
Let’s compare measurements before and after translations, rotations, and reflections.
Required Materials
Activity 3
Required Preparation
None
Corresponding parts are the parts that match up between a figure and its scaled copy. They have the same relative position. Points, segments, angles, or distances can be corresponding.
Point in the first triangle corresponds to point in the second triangle. Segment corresponds to segment .