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Geometry Lesson 1 Examples of Dilations.notebook
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October 20, 2016
Lesson 10: Examples of Dilations
Supplemental Practice: Page 99 #24
Do now:Quiz
Geometry Lesson 1 Examples of Dilations.notebook
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How many points would you need to separate the circle into to draw an accurate dilated image? Page 95
Use Compass
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How many points would you need to separate the circle into to draw an accurate dilated image? Page 95Use Compass
0°160
Geometry Lesson 1 Examples of Dilations.notebook
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How many points would you need to separate the circle into to draw an accurate dilated image? Page 95
0°135
Geometry Lesson 1 Examples of Dilations.notebook
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Would you be able to produce a circle as an image from the number of points used in this example?
Page 95
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What's wrong with using these points?
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What about this image. Does it look like a circle?
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The number of points to dilate that is enough is as many as are needed to produce a dilated image that looks like the original. For curved figures, like this circle, the more points you dilate the better. The location of the points you choose to dilate is also
important.
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How many points would you need to separate the circle into to draw an accurate dilated image? Page 95
Using Calculations
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96
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What can we do to map this new triangle, triangle A'B'C', back to the original triangle? Be as specific as possible!
Page 97
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Reverse a dilation by using a scale factor that
is the multiplicative inverse (reciprocal) of the first scale
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Original Dilation scale factor: 2Scale factor to reverse the dilation:
Original Dilation scale factor: 17
Scale factor to reverse the dilation:
Original Dilation scale factor: 23
Scale factor to reverse the dilation:
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Step 1- Measure the distances between point O and A and point O and A'.
|OA| = 6 units|OA'| = 2 units
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Step 2- Compare the distances and create an equation! You want to now go from A' to A.
|OA| = 6 units|OA'| = 2 units
Think!!! What can I multiply |OA'| by to give me |OA|.
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If a figure is dilated by scale factor, r, to bring the dilated figure back to the original size, we must dilate it by a scale factor of .
If a scale factor is r =6, then the bring a dilated figure back to the original size, the scale factor must equal ________.
(reciprocal)
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Page 97
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Page 98
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