Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
5. Properties of Trapezoids and Kites
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Exercise 54 Page 406

Consider the changes in the diagrams and the changes in the coordinates of the vertices of the triangles to transform â–ł DEF to â–ł PQR.

Example Answer: A reflection over the y-axis and then a dilation with a scale factor 13.

Practice makes perfect

We will identify the similarity transformation that maps the blue preimage to the green image.

We will begin by reflecting the preimage over the y-axis. To do so, we will apply the Coordinate Rules for Reflections. Let's recall the rule, especially the one about reflection over the y-axis!

The Coordinate Rule for Reflection Over the y-Axis

If (a,b) is reflected in the y- axis, then its image is the point (-a,b).


With this information, we will reflect each vertex of △ DEF over the y-axis. (a,b) → (-a,b) D(-3,6) → D'(3,6) E(-3,3) → E'(3,3) F(-9,3) → F'(9,3) Now, we will draw the image of reflection, △ D'E'F'.

Next, we will reduce △ D'E'F' with a scale factor of 13. To do so we will multiply the coordinates of each vertex by 13. This transformation is called dilation with a scale factor of 13. Note that by the Coordinate Rule for Dilation the center of dilation is at the origin, (0,0). (x,y) → (13x,13y) D'(3,6) → P(1,2) E'(3,3) → Q(1,1) F'(9,3) → R(3,1) Finally, we have transformed △ DEF to △ PQR.

Therefore, the similarity transformation is a reflection over the y-axis and then a dilation with a scale factor of 13. Take note that this is just one possible way of doing the similarity transformation, and your answer may vary.