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The ideas in this geometry lesson are taken from the Geometry ebook that I sell at MathMammoth.com. This lesson plan does not contain all the problems the Geometry ebook does. Compass and ruler constructions
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| An equilateral triangle | ||
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| These two points mark the side of the triangle. Start out by drawing a circle using one of those points as a center point and the other one indicating the radius. | ||
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| Can you see what was done in this picture? | The triangle is ready! | |
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Why does it work? Discuss with your teacher! |
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A perpendicular line to a given line |
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An altitude to a triangle [Omitted from the Free lesson plan; available in the ebook.] |
All exercises here are to be done using the compass and ruler only.
1. Draw an equilateral triangle whose sides are this long:
3. Draw any long line on your paper. Then draw a perpendicular line to that line.
5. For each triangle, measure two of its angles and the side between those two angles. Then use that information to copy the triangle to your notebook like we have studied. Then draw an altitude to each triangle..
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An angle bisector - or to draw a line that would divide a given
angle into two equal angles. The prefix 'bi' refers to two, in this case
referring to dividing into two sections, a bisector. [Pictures available in the ebook] |
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| How to draw a line that would divide the angle into two equal angles? (Note: the dotted line in the picture has been 'eyeballed' and is just approximate. We want to draw it exact!) | Draw any circle using B as the center point. Mark the points where that circle intersects the sides of the angle. | What kind of triangle is triangle ABC? Why? | ||
| The angle bisector is actually the ___________________ of the triangle ABC, and of course drawn the same way. |
[Picture omitted from the Free lesson plan; available in the ebook.] |
7. Measure each of these angles, and then copy them to your notebook. Then bisect them.
[Pictures available in the ebook]
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New terms to remember:
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Learn the upper times tables (6s, 7s, 8s, 9s) with fun mnemonic stories. NEW! Receive a free trial download of Times Tales PLUS a free Memory Trigger Ebook. |
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