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Ch 9.5. DG = FH DE ?. D. Complete the proportion. x. FE. G. Suppose DE=15, find x. 3. . . Suppose DE=15, find EG. 12. F. E. 2. 8. H. Find the value of y. 12. 14. 18. . . y + 3. y. Ch 9.5. Learning Target:
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Ch 9.5 DG = FH DE ? D Complete the proportion. x FE G Suppose DE=15, find x. 3 Suppose DE=15, find EG. 12 F E 2 8 H Find the value of y. 12 14 18 y + 3 y
Ch 9.5 Learning Target: I will be able to use proportions to determine whether lines are parallel to sides of triangles. Standard 7.0 Students use theorems involving the properties of parallel lines cut by a transversal. Ch 9.5Proportional Parts
Ch 9.5 midsegment of a triangle A segment of a triangle is called a midsegment when its endpoints are the midpoints of two sides of the triangle. A Midpoint of AC Midpoint of AB B C Vocabulary
Ch 9.5 Theorem 9-6 Concept
Ch 9.5 Since the sides are proportional. In order to show that we must show that Answer: Since the segments have proportional lengths, GH || FE. Determine if Lines are Parallel Example 2
Ch 9.5 A. yes B. no C. cannot be determined Example 2
Ch 9.5 Theorem 9-7 Concept
Ch 9.5 ED = AB Triangle Midsegment Theorem A. In the figure, DE and EF are midsegments of ΔABC. Find AB. 5 = AB Substitution 1 1 __ __ 2 2 Use the Triangle Midsegment Theorem 10 = AB Multiply each side by 2. Answer:AB = 10 Example 3
Ch 9.5 FE = BC Triangle Midsegment Theorem B. In the figure, DE and EF are midsegments of ΔABC. Find FE. FE = (18) Substitution 1 1 __ __ 2 2 Use the Triangle Midsegment Theorem FE = 9 Simplify. Answer:FE = 9 Example 3
Ch 9.5 C. In the figure, DE and EF are midsegments of ΔABC. Find mAFE. By the Triangle Midsegment Theorem, AB || ED. Use the Triangle Midsegment Theorem AFEFED Alternate Interior Angles Theorem mAFE = mFED Definition of congruence mAFE = 87 Substitution Answer:mAFE= 87 Example 3
Ch 9.5 A. In the figure, DE and DF are midsegments of ΔABC. Find BC. A. 8 B. 15 C. 16 D. 30 Example 3
Ch 9.5 B. In the figure, DE and DF are midsegments of ΔABC. Find DE. A. 7.5 B. 8 C. 15 D. 16 Example 3
Ch 9.5 C. In the figure, DE and DF are midsegments of ΔABC. Find mAFD. A. 48 B. 58 C. 110 D. 122 Example 3