5.5 Dilations
I CAN...
Draw dilations of a figure.
Scale Factor­ The ratio of the lengths of two corresponding sides of two similar objects. (Always unit­less, which means must be in the same units) Image
Pre­image
Enlargement­ Scale factor greater than 1
Reduction­ Scale factor less than 1, but greater than 0.
Determine scale factor of a dilation.
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Ex 1A) Copy trapezoid PQRS and point C. Then use a ruler to draw the image of trapezoid PQRS under a dilation with center C and scale factor 3.
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Ex 1B) Which diagram shows the dilation image of ΔLMN with center C and the scale factor is 1 ?
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Ex 2) To create the illusion of a “life­sized” image, puppeteers sometimes use a light source to show an enlarged image of a puppet projected on a screen or wall. Suppose that the distance between a light source L and the puppet is 24 inches (LP). To what distance PP' should you place the puppet from the screen to create a 49.5­inch tall shadow (I'M') from a 9­inch puppet?
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Ex 2 Continued...
24"
9"
x"
49.5"
Step 3) How can we find the missing length?
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Ex 4) Trapezoid EFGH has vertices E(–8, 4), F(–4, 8), G(8, 4) and H(–4, –8). Graph the image of EFGH after a dilation centered at the origin with a scale factor of 1/4. EX 3) Find the scale factor of the dilation in the picture above? Aug 5­1:58 PM
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