Section 5-5
                           The Triangle Inequality




Thursday, March 15, 2012
Essential Questions

                    • How do you use the Triangle Inequality
                           Theorem to identify possible triangles?


                    • How do you prove triangle relationships
                           using the Triangle Inequality Theorem?



Thursday, March 15, 2012
Exercise

                 Draw a triangle with the following side lengths:
                             6 cm, 4 cm, and 10 cm




Thursday, March 15, 2012
Theorem 5.11 - Triangle
                  Inequality Theorem




Thursday, March 15, 2012
Theorem 5.11 - Triangle
                  Inequality Theorem

  The sum of the lengths of any two sides of a triangle must
        be greater than the length of the third side




Thursday, March 15, 2012
Example 1
 Is it possible to form a triangle with the given side lengths?
                     If not, explain why not.
                         1 1      1
                     a. 6 , 6 ,14        b. 6.8, 7.2, 5.1
                         2 2      2




Thursday, March 15, 2012
Example 1
 Is it possible to form a triangle with the given side lengths?
                     If not, explain why not.
                         1 1      1
                     a. 6 , 6 ,14        b. 6.8, 7.2, 5.1
                         2 2      2


                   1   1    1
              No; 6 + 6 <14
                   2   2    2


Thursday, March 15, 2012
Example 1
 Is it possible to form a triangle with the given side lengths?
                     If not, explain why not.
                         1 1      1
                     a. 6 , 6 ,14        b. 6.8, 7.2, 5.1
                         2 2      2

                                              Yes
                   1   1    1
              No; 6 + 6 <14
                   2   2    2


Thursday, March 15, 2012
Example 1
 Is it possible to form a triangle with the given side lengths?
                     If not, explain why not.
                         1 1      1
                     a. 6 , 6 ,14        b. 6.8, 7.2, 5.1
                         2 2      2

                                              Yes
                   1   1    1
              No; 6 + 6 <14
                   2   2    2           5.1 + 6.8 > 7.2



Thursday, March 15, 2012
Example 2
      In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following
                measures cannot be AC? Why not?

                           a. 7   b. 9   c. 11   d. 13




Thursday, March 15, 2012
Example 2
      In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following
                measures cannot be AC? Why not?

                           a. 7   b. 9      c. 11   d. 13

                                  7.2 + 5.2 =




Thursday, March 15, 2012
Example 2
      In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following
                measures cannot be AC? Why not?

                           a. 7   b. 9      c. 11    d. 13

                                  7.2 + 5.2 = 12.4




Thursday, March 15, 2012
Example 2
      In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following
                measures cannot be AC? Why not?

                            a. 7      b. 9       c. 11      d. 13

                                      7.2 + 5.2 = 12.4
                           So the third side must be less than 12.4




Thursday, March 15, 2012
Example 2
      In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following
                measures cannot be AC? Why not?

                            a. 7      b. 9       c. 11      d. 13

                                      7.2 + 5.2 = 12.4
                           So the third side must be less than 12.4
                              d. 13 cannot be a measure for AC


Thursday, March 15, 2012
Example 3
        The towns of Mitarnowskia, Fuzzy-Jeffington, and
      Sheckyville are shown in the map below. Prove that by
     driving from Mitarnowskia to Fuzzy-Jeffington and then
     Fuzzy-Jeffington to Sheckyville is a greater distance than
            driving from Mitarnowskia to Sheckyville.




Thursday, March 15, 2012
Example 3
        The towns of Mitarnowskia, Fuzzy-Jeffington, and
      Sheckyville are shown in the map below. Prove that by
     driving from Mitarnowskia to Fuzzy-Jeffington and then
     Fuzzy-Jeffington to Sheckyville is a greater distance than
            driving from Mitarnowskia to Sheckyville.


                              Let the vertices be F, M, and S.




Thursday, March 15, 2012
Example 3
        The towns of Mitarnowskia, Fuzzy-Jeffington, and
      Sheckyville are shown in the map below. Prove that by
     driving from Mitarnowskia to Fuzzy-Jeffington and then
     Fuzzy-Jeffington to Sheckyville is a greater distance than
            driving from Mitarnowskia to Sheckyville.


                              Let the vertices be F, M, and S.
                                By the Triangle Inequality
                                Theorem, MF + FS > MS.

Thursday, March 15, 2012
Check Your
                           Understanding

                           Look at #1-5 on page 362




Thursday, March 15, 2012
Problem Set




Thursday, March 15, 2012
Problem Set


                           p. 363 #7-33 odd, 43, 53, 57




           "If you can find a path with no obstacles, it probably
                 doesn't lead anywhere." - Frank A. Clark
Thursday, March 15, 2012

Geometry Section 5-5 1112

  • 1.
    Section 5-5 The Triangle Inequality Thursday, March 15, 2012
  • 2.
    Essential Questions • How do you use the Triangle Inequality Theorem to identify possible triangles? • How do you prove triangle relationships using the Triangle Inequality Theorem? Thursday, March 15, 2012
  • 3.
    Exercise Draw a triangle with the following side lengths: 6 cm, 4 cm, and 10 cm Thursday, March 15, 2012
  • 4.
    Theorem 5.11 -Triangle Inequality Theorem Thursday, March 15, 2012
  • 5.
    Theorem 5.11 -Triangle Inequality Theorem The sum of the lengths of any two sides of a triangle must be greater than the length of the third side Thursday, March 15, 2012
  • 6.
    Example 1 Isit possible to form a triangle with the given side lengths? If not, explain why not. 1 1 1 a. 6 , 6 ,14 b. 6.8, 7.2, 5.1 2 2 2 Thursday, March 15, 2012
  • 7.
    Example 1 Isit possible to form a triangle with the given side lengths? If not, explain why not. 1 1 1 a. 6 , 6 ,14 b. 6.8, 7.2, 5.1 2 2 2 1 1 1 No; 6 + 6 <14 2 2 2 Thursday, March 15, 2012
  • 8.
    Example 1 Isit possible to form a triangle with the given side lengths? If not, explain why not. 1 1 1 a. 6 , 6 ,14 b. 6.8, 7.2, 5.1 2 2 2 Yes 1 1 1 No; 6 + 6 <14 2 2 2 Thursday, March 15, 2012
  • 9.
    Example 1 Isit possible to form a triangle with the given side lengths? If not, explain why not. 1 1 1 a. 6 , 6 ,14 b. 6.8, 7.2, 5.1 2 2 2 Yes 1 1 1 No; 6 + 6 <14 2 2 2 5.1 + 6.8 > 7.2 Thursday, March 15, 2012
  • 10.
    Example 2 In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following measures cannot be AC? Why not? a. 7 b. 9 c. 11 d. 13 Thursday, March 15, 2012
  • 11.
    Example 2 In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following measures cannot be AC? Why not? a. 7 b. 9 c. 11 d. 13 7.2 + 5.2 = Thursday, March 15, 2012
  • 12.
    Example 2 In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following measures cannot be AC? Why not? a. 7 b. 9 c. 11 d. 13 7.2 + 5.2 = 12.4 Thursday, March 15, 2012
  • 13.
    Example 2 In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following measures cannot be AC? Why not? a. 7 b. 9 c. 11 d. 13 7.2 + 5.2 = 12.4 So the third side must be less than 12.4 Thursday, March 15, 2012
  • 14.
    Example 2 In ∆ABC, AB = 7.2 and BC = 5.2. Which of the following measures cannot be AC? Why not? a. 7 b. 9 c. 11 d. 13 7.2 + 5.2 = 12.4 So the third side must be less than 12.4 d. 13 cannot be a measure for AC Thursday, March 15, 2012
  • 15.
    Example 3 The towns of Mitarnowskia, Fuzzy-Jeffington, and Sheckyville are shown in the map below. Prove that by driving from Mitarnowskia to Fuzzy-Jeffington and then Fuzzy-Jeffington to Sheckyville is a greater distance than driving from Mitarnowskia to Sheckyville. Thursday, March 15, 2012
  • 16.
    Example 3 The towns of Mitarnowskia, Fuzzy-Jeffington, and Sheckyville are shown in the map below. Prove that by driving from Mitarnowskia to Fuzzy-Jeffington and then Fuzzy-Jeffington to Sheckyville is a greater distance than driving from Mitarnowskia to Sheckyville. Let the vertices be F, M, and S. Thursday, March 15, 2012
  • 17.
    Example 3 The towns of Mitarnowskia, Fuzzy-Jeffington, and Sheckyville are shown in the map below. Prove that by driving from Mitarnowskia to Fuzzy-Jeffington and then Fuzzy-Jeffington to Sheckyville is a greater distance than driving from Mitarnowskia to Sheckyville. Let the vertices be F, M, and S. By the Triangle Inequality Theorem, MF + FS > MS. Thursday, March 15, 2012
  • 18.
    Check Your Understanding Look at #1-5 on page 362 Thursday, March 15, 2012
  • 19.
  • 20.
    Problem Set p. 363 #7-33 odd, 43, 53, 57 "If you can find a path with no obstacles, it probably doesn't lead anywhere." - Frank A. Clark Thursday, March 15, 2012