# Warm Up Simplify each radical. 1. 2. 3. Warm Up Simplify each radical. 1. 2. 3. Find the distance between each pair of points. Write your answer in simplest

radical form. 4. C (1, 6) and D (2, 0) 5. E(7, 1) and F(1, 5) Objectives Apply similarity properties in the coordinate plane. Use coordinate proof to prove figures similar.

Vocabulary dilation scale factor A dilation is a transformation that changes the size of a figure but not its shape. The preimage and the image are always similar.

Scale Factor the ratio of image to its pre-image The ratio of corresponding sides Scale Factor When scale factor is greater than 1, the shape gets bigger

(enlargement). When scale factor is less than 1, but greater than 0, the shape gets smaller (reduction). SCALE FACTOR. 6

2 B A 14 6 3

2 1 C 6 1 0 7

D 3 5 5 1 10 2

Find the coordinates of the dilation image for the given scale factor, k. Example 1: G(0, -2), H(1, 3), and I(4, 1); k = 2 All you do is multiply k to

(x, y). G( , ), H( , ), and I( , ) Find the coordinates of the dilation image for the given scale factor, k. Example 2: L(8, -8), N(0, 16), and M(4, 5); k = 1/4

All you do is multiply k to (x, y). L( , ), N( ,

), and M( , ) k = 1/2 k=2

Example 1: Computer Graphics Application Draw the border of the photo after a dilation with scale factor Example 1 Continued Step 1 Multiply the vertices of the photo A(0, 0), B(0, 4), C(3, 4), and D(3, 0) by Rectangle

ABCD Rectangle ABCD Example 1 Continued Step 2 Plot points A(0, 0), B(0, 10), C(7.5, 10), and D(7.5, 0). Draw the rectangle.

Example 2: Finding Coordinates of Similar Triangle Given that TUO ~ RSO, find the coordinates of U and the scale factor. Since TUO ~ RSO, Substitute 12 for RO, 9 for TO, and 16 for OY.

12OU = 144 OU = 12 Cross Products Prop. Divide both sides by 12. Example 2 Continued U lies on the y-axis, so its x-coordinate is 0. Since OU = 12, its y-coordinate must be 12. The coordinates of

U are (0, 12). So the scale factor is Check It Out! Example 2 Given that MON ~ POQ and coordinates P (15, 0), M(10, 0), and Q(0, 30), find the coordinates of N and the scale factor.

Since MON ~ POQ, Substitute 10 for OM, 15 for OP, and 30 for OQ. 15 ON = 300 ON = 20 Cross Products Prop. Divide both sides by 15.

Check It Out! Example 2 Continued N lies on the y-axis, so its x-coordinate is 0. Since ON = 20, its y-coordinate must be 20. The coordinates of N are (0, 20). So the scale factor is Lesson Quiz: Part I

1. Given X(0, 2), Y(2, 2), and Z(2, 0), find the coordinates of X', Y, and Z' after a dilation with scale factor 4. X'(0, 8); Y'(8, 8); Z'(8, 0) 2. JOK ~ LOM. Find the coordinates of M and the scale factor. Lesson Quiz: Part II 3. Given: A(1, 0), B(4, 5), C(2, 2), D(2, 1), E(4, 9), and F(8, 3)

Prove: ABC ~ DEF Therefore, by SSS ~. and ABC ~ DEF