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No Clickers. Bellwork. Perform a glide reflection of <1,4> and over line y=x for the points A: (-4,2), B :(-22,-3) and C:( 0,2). Bellwork Solution. Perform a glide reflection of <1,4> and over line y=x for the points A: (-4,2), B :(-22,-3) and C:( 0,2). Section 9.7.
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No Clickers Bellwork • Perform a glide reflection of <1,4> and over line y=x for the points A: (-4,2), B:(-22,-3) and C:( 0,2)
Bellwork Solution • Perform a glide reflection of <1,4> and over line y=x for the points A: (-4,2), B:(-22,-3) and C:( 0,2)
Section 9.7 Identify and perform Dilations
The Concept • For our last section of chapter 9 we’re going to revisit Dilations • For the most part, our understanding of these transformations was relatively complete. We are primarily going to revisit the process and discuss how we can perform dilations with matrices
Review • Dilations • Scaling of an object by the same factor in all directions • Similarity transformation • Not an Isometry
Coordinate Notation • For similicity, we prefer to be able to notate for dilations • For dilations centered at the origin • (x,y)(kx,ky), where k is a scale factor • If 0<k<1, reduction • If k>1, enlargement • We can also find k from two objects by dividing the length of a side of the image by the length of the corresponding side of the preimage
Drawing a Dilation • Draw a dilation of an object with vertices (4,6), (2, 4) & (6,-6) using a scale factor of 1/2
Example Draw a dilation of scale factor 2 for ABCD with vertices A(2,2), B(4,2), C(4,0), D(0,-2).
Scalar Multiplication • Because in a dilation all coordinates are scaled by the same number we can use a process called scalar multiplication of a matrix to show the new coordinates • Scalar multiplication is the “distribution” of a value to interior values of a matrix • e.g. a dilation of scale factor 4 on the previous set of points Scale factor
Example • We can also combine transformations • Perform a combination of transformations by translating over the vector <-4,2> then dilating by a factor of ½. • A: (3,1), B: (2,0), C: (-2,5)
Homework • 9.7 Exercises • 1-6, 15-22, 26, 36, 37
Most Important Points • Definition of Dilation • Bounds for the k scalar • Performing Dilations • Using scalar multiplication to perform dilations • Combining transformations