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8.4 Similar Triangles

8.4 Similar Triangles. Number Talk. The scale on a map is 6cm : 2kn. If the distance between two cities is 8kn, how far apart in cm are the two cities on the map?. In Chemistry Class there is a girl to boy ratio of 5 : 8. If there are a total of 39 students, how many boys are there?.

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8.4 Similar Triangles

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  1. 8.4 Similar Triangles

  2. Number Talk The scale on a map is 6cm : 2kn. If the distance between two cities is 8kn, how far apart in cm are the two cities on the map? • In Chemistry Class there is a girl to boy ratio of 5 : 8. If there are a total of 39 students, how many boys are there? In Geometry Class, the girl to boy ratio is 8 to 6. If there are a total of 42 students, how many girls are there?

  3. How did we do?

  4. Postulate 25 • Angle-Angle (AA) Similarity Postulate If two angles of one triangle are congruent to two angles of another triangle, then the two triangles are similar.

  5. Similar Triangles • Given the triangles are similar. Find the value of the variable. )) m )) ) 6 8 11m = 48 ) 11

  6. Let’s Try

  7. Similar Triangles • Given the triangles are similar. Find the value of the variable. Left side of sm Δ Base of sm Δ Left side of lg Δ Base of lg Δ = 6 5 > 2 6h = 40 > h

  8. ∆ABC is similar to ∆DBE. A 5 D y 9 x B C E 8 4

  9. Warm Up: Determine whether the triangles are similar. 6 32° 33° 9 18 No, because two angles of one triangle are not congruent to two angles of another triangle.

  10. Determine whether the triangles are similar. 60° 60° 60° 60° Yes, because two angles of one triangle are congruent to two angles of another triangle.

  11. Given two triangles are similar, solve for the variables. 2b - 8 a + 3 14 15 16 ) ) 10 15(a+3) = 10(16) 15a + 45 = 160 15a = 115

  12. Decide whether two triangles are similar, not similar, or cannot be determined. A 92° 31° S 47° 41° 92° 57° S + 92 + 41 = 180 S + 133 = 180 S = 47 A + 92 + 57 = 180 A + 149 = 180 A = 31 Not similar

  13. 2 Practice Problems • For each problem. Show your solutions mathematically as well as explain what you did in plain English. • For Example • “When setting up the proportion 4/x = 15/5 I knew that EB corresponds with DC and EA corresponds with AD.”

  14. Take Exit Slip on IPAD • Test ID: 0881886769 • Re Take Yesterday’s Formative: 6461882153

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