1. Ratios in Similar Polygons p. 244 in your book
Thursday August 8th 2013
Unit 1; Module 8-1
Ratios in Similar Polygons
p. 244 in your book
Holt McDougal Geometry
Holt Geometry

2. Warm Up / Prior Knowledge
1. If ∆QRS  ∆ZYX, identify the pairs of congruent angles and the pairs of congruent sides.
Solve each proportion.
Q  Z; R  Y; S  X; QR  ZY; RS  YX; QS  ZX
x = 9
x = 18

3. Objectives Identify similar polygons.
Apply properties of similar polygons to solve problems.

4. Vocabulary 1) congruent (review from Alg I CC)
having the same size & shape, denoted by
2) similarity ratio
the ratio of the lengths of the corresponding sides of 2 similar polygons
3) 3rd Angle Theorem
if 2 angles of one triangle are congruent to 2 angles of
another triangle, then the 3rd angles are also congruent

5. 4) Figures that are similar (~) have the same shape but not necessarily the same size.

6. 5) Similar polygons
2 polygons whose corresponding angles are congruent and whose corresponding side lengths are proportional

7. Example 1: Describing Similar Polygons
Identify the pairs of congruent angles.
0.5
N  Q and P  R.
By the Third Angles Theorem, M  T.

8. Example 1: Describing Similar Polygons
Identify the pairs of corresponding sides.
0.5

9. TRY THIS ON YOUR OWN! Example 1
Identify the pairs of congruent angles and corresponding sides.
Angles: B  G , C  H , A  J.
Sides:

10. Tonight’s HW Assignment
At home, everyone needs to log on to MY eCLASS and make sure you can get into the online textbook