This lesson begins with a Do Now, asking students to review how to graph a triangle and quadrilateral on a coordinate plane. This is a good opportunity for teachers to ensure that students have a strong knowledge of graphing points, labeling points and more practically, have graph paper :) During Do Nows, my students work independently and check their work with their partner. I then usually ask student volunteers to post their answers on the SmartBoard in my classroom, and we review any questions or concerns before going over the objective and agenda for the day. You may want to stop and review graphing points before moving on, if students are struggling with this Do Now.
Students will be provided with scaffolded notes (if possible) and will watch a 1986 version of the trailer for the movie Transformers. Students will have a chance to record any transformations that they see, and also make note of graphics for this older video. Teachers may want to model how to keep track of transformers - for example, robot --> transformer. When teachers review pre-image and image vocabularly, this is a great connection to make (i.e. a robot turned into a transformer, not a transformer turned into a robot - order matters!)
Turn and talk:
Students can turn and talk to compare their findings and if time remains, teachers can ask students to describe the graphics and animation. Teachers should try to emphasis that the transformers differ from the transformations that will be learned in class. A transformation is 1 move not a change in shape (like a transformer). Typically, my students will connect the idea of transformers with transformations because they both change. However, now is a great time for teachers to focus on the real definition of transformation - a move for a shape (not a complete change).
Review of Activity:
After trying to reflect figures about the x and y-axis, teachers may want to ask student volunteers to write their work and graphs on the board. Then, teachers can ask students to guess the rule for each reflection.
The most challenging aspect of this lesson is asking students to determine the rule for y=x axis. As a scaffold teachers may want to help students first draw line y=x onto their graph as a starting point. From here, teachers can further support students by asking students how they completed the other reflections, and more specifically, how did students know where to put their new image points? Teachers can also introduce the idea of equidistant as well to help scaffold students' discovery.
After reviewing all three cases, students can work in small groups on the practice examples provided and then move onto the worksheet provided. If possible, teachers may want to provide colored pencils or white boards with graphs as a manipulative. Teachers can help students to summarize the lesson by asking review questions like,
- How did you discover the rules for reflecting points about a line?
- Do we need to memorize the rules for reflecting about the x-axis, y-axis and y=x line?
- Why does it make sense that for y=x, we simply switch the x and y value? Or simiarly, why do we just negate the x-values to reflect about the y-axis?
- We learned a lot of vocabularly today, can someone review pre-image and image for us? What is a line of symmetry?
At the end of class, teachers may want to have students present 2-3 questions from worksheet to class as a review. Then, before, students leave teachers can have an exit ticket for students. Some exit ticket questions could ask students to write the rules for reflection about x-axis, y-axis and y=x line. Another exit ticket may ask students to pick a letter (like K), identify the pre-image and image and then reflect this shape about the y-axis.
The homework for this lesson would be HW #41 found on the homework sheet provided which is aligned to the Glencoe Geometry book. Teachers should focus on a homework assignment that ask students to graph polygons and complete reflection problems