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IM Geo.1.11 Lesson: Defining Reflections

Autor:GeoGebra Classroom Activities, IM Algebra 1, Geometry, Algebra 2

Which one doesn’t belong?

Figure 1Figure 2

Figure 3Figure 4


Your teacher will assign you either a problem card or a data card in the applet below. Do not show or read your card to your partner.

If your teacher gives you the data card:If your teacher gives you the problem card:
  1. Silently read the information on your card.
  2. Ask your partner “What specific information do you need?” and wait for your partner to ask for information. Only give information that is on your card. (Do not figure out anything for your partner!)
  3. Before telling your partner the information, ask “Why do you need to know (that piece of information)?”
  4. Read the problem card, and solve the problem independently.
  5. Share the data card, and discuss your reasoning.

  1. Silently read your card and think about what information you need to answer the question.
  2. Ask your partner for the specific information that you need.
  3. Explain to your partner how you are using the information to solve the problem.
  4. When you have enough information, share the problem card with your partner, and solve the problem independently.
  5. Read the data card, and discuss your reasoning.

Kiran started reflecting triangle CDE across line m. So far, he knows the image of D is D' and the image of E is E'.

  • Annotate the diagram to show how he reflected point .
  • Use straightedge and compass moves to determine the location of . Then lightly shade in triangle .
  • Write a set of instructions for how to reflect any point  across a given line .

Elena found C' incorrectly:

Elena's Diagram Elena is convinced that triangle  “looks fine.” Explain to Elena why her  is not a reflection of point  across line .

Using your response from the correct location of C'

  • Draw the line .
  • Reflect triangle  across line .
  • Label the image .
Find a single rigid motion that takes  to .

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