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Inequalities in One Triangle. Geometry CP2 (Holt 5-5) K. Santos. Theorem 5-5-1. In a triangle, larger angle opposite longer side Y X Z If XZ > XY then m<Y > m<Z. Example. List the angles from largest to smallest. A 10 B
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Inequalities in One Triangle Geometry CP2 (Holt 5-5) K. Santos
Theorem 5-5-1 In a triangle, larger angle opposite longer side Y X Z If XZ > XY then m<Y> m<Z
Example List the angles from largest to smallest. A 10 B 5 8 C Largest angle: <C <A Smallest angle: <B
Theorem 5-5-2 In a triangle, longer side is opposite larger angle A B C If m<A>m<B then BC>AC
Example List the sides from largest to smallest. A 5060 B C Find the missing angle first: 180 – (50 +60) m < C = 70 Largest side: Smallest side:
Triangle Inequality Theorem (5-5-3) The sum of the lengths of any two sides of a triangle is greater than the length of the third side. X Y Z XY + YZ> XZ YZ + ZX >YX ZX + XY>ZY add two smallest sides together first
Examples: Can you make a triangle with the following lengths? • 4, 3, 6 4 + 3 > 6 add the two smallest numbers 7 > 6 triangle • 3, 7, 2 3 + 2 > 7 5 > 7 not a triangle • 5, 3, 2 3 + 2 > 5 5 >5 not a triangle
Example: The lengths of two sides of a triangle are given as 5 and 8. Find the length of the third side. 8 – 5 = 3 5 + 8 = 13 The third side is between 3 and 13 3 < s < 13 where s is the missing side