Lesson 10

The purpose of this optional lesson is for students to use the attributes of figures (symmetry, equal side lengths, right angles) to reason about angle measurements.

Previously, students analyzed the attributes of two-dimensional figures and used them to find side lengths and perimeters. In this lesson, students use the attributes of figures to find unknown angle measurements and to practice drawing line-symmetric shapes. Both activities in the lesson deepen students’ understanding of line symmetry. They also allow students to apply knowledge of angles from an earlier unit and integrate it with newer ideas from this unit. Because the work here is not required by the standards, however, this lesson is optional.

Today’s lesson presented many opportunities for divergent reasoning strategies. Think about which students haven’t shared their strategies in class lately. Were there missed opportunities to highlight their thinking during recent lessons? How can you take advantage of those opportunities when they arise?