# Lesson 5

Simetría de figuras (parte 2)

### Lesson Purpose

The purpose of this lesson is for students to identify figures with line symmetry and to complete line-symmetric figures.

### Lesson Narrative

Previously, students learned to identify figures with line symmetry and drew lines of symmetry. In this lesson, students deepen their understanding of symmetry by reasoning about what the whole figure would look like when given half of a figure and a line of symmetry.

The work of this lesson helps students develop mental images of figures with lines of symmetry. Students also consider how to use what they know about drawing line segments, points, and angles to complete their drawings. They make strategic decisions about how to use available tools to complete the shapes or justify how they know their figures are symmetrical (MP5). Students may copy the figure to another piece of paper, and follow with folding, cutting, or tracing. They may also use rulers or protractors to measure distances and angles.

• Representation
• MLR8

### Learning Goals

Teacher Facing

• Identify figures with line symmetry and draw lines of symmetry on two-dimensional figures.

### Student Facing

• Dibujemos algunas figuras que tienen líneas de simetría.

### Required Materials

Materials to Gather

Materials to Copy

• Two Symmetrical Figures

### Required Preparation

Activity 3:

• Create a set of triangle cutouts from the blackline master for each group of 2.

### Lesson Timeline

 Warm-up 10 min Activity 1 15 min Activity 2 20 min Activity 3 10 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

What connections did students make between the different strategies shared? What questions did you ask to help make the connections more visible?

### Suggested Centers

• Symmetrical Designs (4), Stage 1: Lines of Symmetry (Addressing)
• Which One? (K–5), Stage 4: Grade 3 Shapes (Supporting)
• Can You Draw It? (1–5), Stage 4: Area and Perimeter (Supporting)