Students know the definition of reflection and perform reflections across a line using a transparency.

Students show that reflections share some of the same fundamental properties with translations (e.g., lines map to lines, angle and distance preserving motion, etc.). Students know that reflections map parallel lines to parallel lines.

Teacher and Student versions of full lesson from engageNY

Students know that for the reflection across a line L, then every point P, not on L, L is the bisector of the segment joining P to its reflected image P'.

Students learn the precise definition of a reflection.

Students construct the line of reflection of a figure and its reflected image. Students construct the image of a figure when provided the line of reflection.

Teacher and Student versions of full lesson from engageNY

What if you wanted to find the center of rotation and angle of rotation for the arrows in the international recycling symbol below? It is three arrows rotated around a point. Let’s assume that the arrow on the top is the preimage and the other two are its images. Find the center of rotation and the angle of rotation for each image. After completing this Concept, you'll be able to answer these questions.

Lessons, videos, exercises, and text from CK-12. Other lesson units available as well.