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9.2/9.3 Similar Triangles and Proportions. C. B. A. D. E. Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. Warm-up (IN). 1. Name the triangles that appear to be similar.
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9.2/9.3 Similar Triangles and Proportions C B A D E Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. Warm-up (IN) 1. Name the triangles that appear to be similar. Assume the triangles in #1 are similar. 2. Write 2 true proportions. 3. If AB=6, AE=8 and AC=7, find AD. 4. If CD=12, AD=15 and BE=10, find AE.
Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. Notes • 3 ways to prove triangles are similar! AA Similarity • 2 Corresponding angles are congruent SAS Similarity • 2 Corresponding sides are in proportion • The included angle is congruent SSS Similarity • 3 Corresponding sides are in proportion
Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. EX 1 – H L K N M CKC p. 456!
Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. Triangle Proportionality Thm If a segment is // to one side of a triangle and intersects the other 2 sides, then it divided those sides proportionally. D A E C N
Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. Midsegment Thm If the midpoints of 2 sides of a triangle are joined by a segment, then L the segment is // to the 3rd side and half as long H A G U Properties of Proportions See p. 463
Learning Objective: To use special rules to prove triangles are similar and to write proportions to find measures in similar figures. EX 2 – Find each value D 6 A 9 E C N CKC p. 464 on paper!
Out – Describe 3 ways to show two triangles are similar. Summary – Now I’m thinking… POW!! HW – p. 456 #1-7, p. 464 #1-6,14-16,21