# GBK Geometry - PowerPoint PPT Presentation

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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?

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GBK Geometry

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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