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Engage students with warm-up activities, review key concepts, and introduce area proofs in a structured classroom session. Includes parallelogram proof demonstration and homework assignments. Encourage participation and critical thinking. Prepare students for future lessons.
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GBK Geometry Jordan Johnson
Today’s plan • Greeting • Warm-up • Review Proof Work • Area Proofs • Homework / Questions • Clean-up
Warm-up: Area • Find the areas of the brown polygons: 7 12 5 4 4 9 8 6 4 2 12
Review • Questions on Asg #60 or #61? • Questions regarding the parallelogram proof?
Reminder: Open Problem:Cube Dissection • Suppose you have a 3” x 3” wooden cube and want to saw it into twenty-seven 1” x 1” cubes. • What is the minimal number of cuts needed?
Parallelogram Area • Given: Parallelogram WXYZ with base WZ = b and height h (from that base). • Prove: AWXYZ = bh
Area Formulas • Area of a triangle = ½ bhwhere b is any side and h is the altitude to that side • Area of a parallelogram = bhwhere b is any side and h is the altitude to that side • Area of a trapezoid = ½(b1 + b2)hwhere b1 and b2 are the bases and h is the altitude
Homework • Log 25+ minutes: • Start the trapezoid area proof • Tomorrow, bring in at least the proof setup and either (1) a complete proof, or (2) a partial proof and questions • Then, maybe: • Asg #60 or #61 • Khan Academy recommendations
Clean-up / Reminders • Pick up all trash / items. • Push in chairs (at front and back tables). • See you tomorrow!