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5.5: Inequalities in Triangles. Objectives: To use inequalities involving angles of triangles and to use inequalities involving sides of triangles. Comparison Property of Inequality. If a = b + c and c ≠ 0 , then a > b Apply this to the Triangle Exterior Angle Theorem: Therefore:.
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5.5: Inequalities in Triangles Objectives: To use inequalities involving angles of triangles and to use inequalities involving sides of triangles
Comparison Property of Inequality If a = b + c and c ≠ 0, then a > b Apply this to the Triangle Exterior Angle Theorem: Therefore: 2 3 1
Why is 3 1 4 2
Theorem If 2 sides of a triangle are not congruent, then the larger angle lies opposite the longer side Y If XZ > XY, then X Z
Theorem If 2 angles of a triangle are not congruent, then the longer side lies opposite the larger angle B If , then BC > AC C A
Examples 1. List the angles in order from smallest to largest. 2. List the angles in order from largest to smallest in ∆ABC with AB = 15, BC=20, and AC = 30. J 6 G 8 7 C
Examples 1. List the sides in order from longest to shortest. A 40 S 55 85 C
List the sides in order from shortest to longest in ∆TFK with
Triangle Inequality Theorem The sum of lengths of any 2 sides of a ∆ is greater than the length of the 3rd side. B AB + BC > AC AC + BC > AB AB + AC > BC C A
Example • A triangle has sides of lengths 8 cm and 10 cm. Describe the possible lengths of the third side. The possible lengths will be greater than the difference and less than the sum of the 2 given sides
Can a triangle have sides with the given lengths? Explain. • 6 ft, 8 ft, 2ft • 10 in, 15 in, 20 in • 12cm, 6cm, 4 cm