http://www.ck12.org Chapter 5. Relationships with Triangles
Vocabulary
Anisosceles triangleis a triangle with two congruent sides. The congruent sides are called thelegsand the third
side is called thebase. TheTriangle Inequality Theoremstates that to make a triangle, two sides must add up to be
greaterthan the third side.
Guided Practice
Do the lengths below make a triangle?
- 4.1, 3.5, 7.5
- 4, 4, 8
- 6, 7, 8
Answers:
Use the Triangle Inequality Theorem. Test to see if the smaller two numbers add up to be greater than the largest
number.
- 1 + 3. 5 > 7 .5. Yes this is a triangle because 7. 6 > 7 .5.
- 4+ 4 =8. No this is not a triangle because two lengthscannot equalthe third.
- 6+ 7 >8. Yes this is a triangle because 13>8.
Explore More
Determine if the sets of lengths below can make a triangle. If not, state why.
- 6, 6, 13
- 1, 2, 3
- 7, 8, 10
- 5, 4, 3
- 23, 56, 85
- 30, 40, 50
- 7, 8, 14
- 7, 8, 15
- 7, 8, 14.99
If two lengths of the sides of a triangle are given, determine the range of the length of the third side.
- 8 and 9
- 4 and 15
- 20 and 32
- 2 and 5
- 10 and 8
15.xand 2x - The legs of an isosceles triangle have a length of 12 each. What can you say about the length of the base?