5. Dilations
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To obtain the image of a vertex after a dilation with scale factor k, multiply its coordinates by k.
W'(- 1, - 32), X'(- 1,2), Y'(1,2), Z'(1, - 32)
A dilation can be an enlargement, a reduction, or the same size as the preimage. Which type of dilation it is depends on the value of the scale factor k.
Enlargement | k>1 |
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Reduction | 0 |
Same | k=1 |
ccc Preimage & & Image [0.5em] (x,y)& ⇒ & ( kx, ky) Now, let's find the coordinates of the vertices of WXYZ after a dilation with a scale factor k= 14.
Dilation With Scale Factor k= 14 | ||
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Preimage | Multiply by k | Image |
W(- 4,- 6) | ( 1/4(- 4), 1/4(- 6)) | W'(- 4/4,- 6/4)=(- 1,- 3/2 ) |
X(- 4,8) | ( 1/4(- 4), 1/4(8)) | X'(- 4/4,8/4)=(- 1,2 ) |
Y(4,8) | ( 1/4(4), 1/4(8)) | Y'(4/4,8/4)=(1,2 ) |
Z(4,- 6) | ( 1/4(4), 1/4(- 6)) | Z'(4/4,- 6/4)=(1,- 3/2 ) |