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5.2 Inequalities and Triangles. What you’ll learn: To recognize and apply properties of inequalities to the measure of angles of a triangle. To recognize and apply properties of inequalities to the relationships between angles and sides of a triangle. Definition of Inequality.
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5.2 Inequalities and Triangles What you’ll learn: To recognize and apply properties of inequalities to the measure of angles of a triangle. To recognize and apply properties of inequalities to the relationships between angles and sides of a triangle.
Definition of Inequality For any real numbers a and b, a>b iff there is a positive number c such that a=b+c.
Properties if InequalitiesFor all numbers a, b, and c Comparison Property a<b, a=b, or a>b Transitive Property: if a<b and b<c, then a<c if a>b and b>c, then a>c Addition/Subt: If a>b then a+c>b+c and a-c>b-c If a<b, then a+c<b+c and a-c<b-c Mult./Div: If c>0 and a<b, then ac<bc and If c>0 and a>b then ac>bc and If c<0 and a<b then ac>bc and If c<0 and a>b then ac<bc and
Theorems Theorem 5.8 Exterior Angle Inequality TheoremIf an angle is an exterior angle of a triangle, then its measure is greater than the measure of either of its corresponding remote interior angles. 1>2, 1>3 Theorem 5.9 If one side of a triangle is longer than another side, then the side opposite the longer side has a greater measure than the angle opposite the shorter side. If BC>AB, then 1>3 2 1 3 A 1 C B 2 3
Theorem 5.10 If one angle of a triangle has a greater measure than another angle, then the side opposite the greater angle is longer than the side opposite the lesser angle. If C>A, then AB>BC. B A C
Examples Which angle has the greatest measure? 1>3 1>4 4=5 1>5 2<90 1>2 Use the exterior angle inequality to list all of the angles that satisfy the stated condition. All angles whose measure are less than m14 4,11,9,3,2,6,7 All angles whose measures are greater than m15 10,16,15,17,12 5 17 14 4 16 4 5 15 3 6 11 1 10 3 2 12 9 2 1 7 8
Determine the relationship between the measures of the given angles RSU____SUR TSV____STV RSV____RUV R 7 S 9 T 5 8 3 4 V U 6
Given: JMJL, JLKLProve: m1>m2 L 2 • JMJL, JLKL • KLJK MJLM • 1>LKJ LJK>2 • 1>LKJ • Given • Isos. Triangle theorem • Ext. angle ineq. thm • substitution 1 M K J