Lesson 1: 3-1: Reflections

1. How can you use tracing paper or patty paper to check that you have drawn a reflection properly?
2. How can you use a ruler to check your work?
3. When would a protractor be useful?
4. What other tool can help you visualize a reflection?

Line of Reflection

G.CO.4
Develop definitions of rotations, reflections, and translations in terms of angles, circles, perpendicular lines, parallel lines, and line segments.
G.CO.5
Given a geometric figure and a rotation, reflections, or translation, draw the transformed figure. Specify a sequence of transformations that will carry a given figure onto another.

A reflection is a congruence transformation or an isometry. Figures may be reflected in a point, a line, or a plane. Reflections can occur in the coordinate plane, with coordinates assigned to each point in the image and preimage.
Mathematically proficient students consider the available tools when solving a mathematical problem.

Notice in a water reflection that the distance a point lies above the water line appears the same as the distance its image lies below the water.

Students approaching grade level can be given practice problems in small groups to work with other students or directly with the teacher.
Students beyond grade level can make deeper connections in the following way: students can work together to come up with examples of reflections in nature and in everyday objects. With these examples, they should be able to identify the lines of reflection and lines of symmetry.

Formative Assessment