The document discusses similar triangles and how to determine if triangles are similar. It explains that similar triangles have congruent angles, while congruent triangles have both congruent angles and sides. It provides examples of using the Angle-Angle similarity criterion to determine if triangles are similar and setting up ratio proportions to calculate missing sides of similar triangles. The lesson objectives are to apply properties of similar triangles and prove that triangles are similar.

1. Similar Triangles Focus – Apply the properties of similar triangles and tomorrow, prove that triangles are similar. Lesson 8-3 WA State Standards: G.3.A and G.3.B

2. Congruent Triangles …have matching angles that are congruent. …have matching sides that are congruent. A B C D F E 100° 35° 45° 115 ft 150 ft 100 ft 150 ft 115 ft 100 ft 35° 100° 45°

3. Congruent Triangles …have matching angles that are congruent. …have matching sides that are congruent. A B C D F E 100° 35° 45° 115 ft 150 ft 100 ft 150 ft 115 ft 100 ft 35° 100° 45°

8. Are they similar? Use Angle/Angle or AA Similarity . Two congruent angles show triangles are similar.

10. Is ABC similar to AEF? A E F C B Sometimes it helps to separate the two triangles and look at each angle separately.

16. Is ABC similar to AEF? If so, what Is the missing side? y 15 16 x 12 12 A B C E F

17. It often helps to separate the two attached triangles. y 15 16 x 12 12

18. Prove: A line drawn from a point on one side of a triangle parallel to another side forms a triangle similar to the original triangle.

23. Solve by using proportions 4 ft 6 ft 5 ft x

24. Assign: 453: 9; 14, 16, 21a, 23, 26 457: 5-7