Section 4.8.notebook
March 01, 2011
Section 4.8: Dilations
dilation
the image produced by enlarging or reducing a figure
will always be similar to the original figure
scale factor of dilation
the ratio of a length on the image to a length on the original figure
Dilations on a coordinate plane:
­To find the coordinates of the vertices of an image after a dilation with center (0, 0), multiply the x­coordinate and y­coordinate by the scale factor.
Example: A(­2, 3)
After a dilation with a scale factor of 2, the image would
be A'(­4, 6).
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Section 4.8.notebook
March 01, 2011
2. Graph ΔJKL with vertices J(3, 8), K(10, 6), and L(8, 2).
a. Find the coordinates of the image after a dilation with a scale factor of 3.
b. Find the coordinates of the image after a dilation with a scale factor of 1/3.
enlargement
a dilation with a scale factor greater than 1
reduction
a dilation with a scale factor between 0 and 1
3. Quadrilateral V'Z'X'W' is a dilation of quadrilateral VZXW. Find the scale factor of the dilation, and classify it as an enlargement or a reduction.
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4. Triangle A'B'C' is a dilation of ΔABC. Find the scale factor of the dilation, and classify it as an enlargement or a reduction.
5. Find the vertices of polygon H'J'K'L' after polygon HJKL is dilated using a scale factor of 2. Then graph both polygons
H(­1, 3)
J(3, 2)
K(2, ­3)
L(­2, ­2)
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Section 4.8.notebook
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6. Graph ΔMNO with vertices M(3, ­1), N(2, ­2), and O(0, 4). Then graph its image ΔM'N'O' after a dilation with a scale factor of 3/2.
7. The pupil of Josh's eye is 6 millimeters in diameter. His doctor uses medicine to dilate his pupils by a factor of 3/2. Find the new diameter once his pupil is dilated.
8. Dana uses an image of his dog as the wallpaper on his computer desktop. The original image is 5 inches high and 7 inches wide. If his computer scales the image by a factor of 5/4, what are the dimensions of the dilated image?
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