Outline: “cutting cubes, and observation of the cut surfaces”
... Learning activities 
... Teacher's instructions/guide 
... Evaluation (expected student responses)
Regarding the necessary software data for using "Cabri 3D File" and "Flash Movie" on the pages, please review [Installing necessary software] .
... Learning activities ... Teacher's instructions/guide ... Evaluation (expected student responses) Regarding the necessary software data for using "Cabri 3D File" and "Flash Movie" on the pages, please review [Installing necessary software] .
Learning content
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Through making stamps by cutting cubic rubber erasers, observe the produced shapes of the cut surfaces. | ||||
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While actually cutting models, concretely show how to create the stamps. | ||||
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Show actual objects cut out in the form of such figures as a regular triangle and a hexagon. | ||||
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Set learning as observation of the cut area when the cube is cut.
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Observe while individually operating Cabri 3D. | ||||
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Respond to any students puzzled using the computer. | ||||
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Request students to think aboutwhere the cut areas' sides will appear. | ||||
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Notice that various shapes can be produced according to cutting method, and that there are shapes that can never be created. | ||||
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Regarding the shapes that cannot be created, think about why. | ||||
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Reconfirm the method of changing observation direction (viewpoint) as needed, and request observation from various directions with regard to where the same cutting method was used. | ||||
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Let the students focus on the types of positional relation ship s that the surfaces of the cube have with each other. | ||||
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Willingly u ndertake the cutting of the cube, and summarize anything that w as noticed through observation. | ||||
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Based on the cutting experience, describe that a regular pentagon can never be created. |
Expected responses from the students
| ア | If the cube is used as a stamp as it is, it is a regular square. |
| イ | When a corner is cut off, a triangle can easily be created. |
| ウ | A circle can never be created. |
| エ | It is definitely possible to know the shape that will be created using various cutting methods and by then observing the shape of the cut area. |
| オ |
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| カ | The meaning of cutting through a plane is easy to underst an d. |
| キ | Lines are shown where the cut plane surfaces and the cube's sides cross. |
| ク |
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| ケ | The shapes shown as stamps coincide with the shapes of the cut area seen from the anterior. |
| コ | Triangle-shaped cut areas appear to be acute triangles only . |
| サ |
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