This activity serves several goals. Students continue to practice visualizing and drawing a complete shape given a line of symmetry and one half of the shape. As they do so, they practice drawing angles of certain measurements. Students also use symmetry to reason about unknown angle measurements in two-dimensional figures.

For the drawing portion of the activity, assign a different figure for each group member to start with and ask students to draw as precisely as possible (MP6). Provide access to protractors and patty paper (MP5). Most students are likely to find Andre’s figure the most challenging to draw. Differentiate the starting drawing for each student as needed.

• Display the drawings that students completed and select students to share how they found the angles inside each figure.
• Highlight that lines of symmetry can be used to identify angles that have the same size as a given angle, or angles that are twice the size of a given angle.

In this activity, students apply their understanding of symmetry and knowledge of angles to find angle measurements in a more complex line-symmetric figure. Students use what they know about the measurement of a straight angle and the measurement of a full rotation of a ray around a point to find the unknown angles. As needed, review the measurements of benchmark angles (, , ) before the activity.

• Invite students to share their responses and reasoning.
• Highlight that:
  • Angles A and D are each part of a straight angle, so each can be found by subtracting the adjacent angle measure from 180.
  • Angle E and the two angles one either side of it make a full turn or .
• Consider asking: “¿Qué otros ángulos pueden encontrar dentro o alrededor del diagrama del pez?” // “Which other angle measurements in or around the fish diagram can you find?” If time permits, encourage students to find as many as they can.