# Sec 1-4 Concepts: Classifying Angles Objectives: Given an angle, name, measure and classify it as measured by a s.g.

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Sec 1-4 Concepts: Classifying Angles Objectives: Given an angle, name, measure and classify it as measured by a s.g.

Example 1: Name the <s in the figure H O G S 1 2 <HOS<SOH <1<SOG <GOS<2 <HOG<GOH

Classify the angle with the given measure as acute, obtuse, right or straight. m<T = 90m<Y = 32 m<X = 180m<A = 160 right acute straight obtuse

Use a protractor to measure the angle. Then classify it. 1. 2. 101 131

Example 3: Find the indicated angle measure 120 60 a bc e d f g 15

Example 4: For each city on the polar map, estimate the measure of <BOA where B is on the Prime Meridian (0۫ Longitude), O is the North Pole and A is the City Clyde River, CanadaFairbanks AlaskaOld Crow Canada Reytjavik IcelandAngmagssalik GreenlandTuktoyaktuk, Cananda About 69 About 148 About 140 About 21 About 38About 133

Angle Addition Postulate If P is in the interior of <RST, then m<RSP +m<PST = m<RST R S P T 50° 60° Example 5:Find the m<RST 50 + 60 = 110°

Example 6: Use the angle addition postulate to solve for x. Then find the measure of each angle. O P R Q (X+4) + (2x-2) = 26 3x+2=26 3x=24 X=8 m<POQ = 8+4 = 12 m<QOR = 2(8)-2= 14 m<POR = 26 A.

Example 6 cont.: Use the angle addition postulate to solve for x. Then find the measure of each angle. O P R Q (3X+7) + (5x-2) = 61 8x+5=56 8x=56 X=7 m<POQ = 3(7)+7 = 28 m<QOR = 5(7)-2=33 m<POR = 61 B.

Example 7: JK bisects < HJL. Given that m<HJL=42°, what are the measures of <HJK and <KJL? H J L K 42 m<HJK and m<KJL must each be half of 42. m<HJK and m<KJL = 21

Example 8: BD bisects <ABC. Find the value of x. C A B D (5x+5) (6x-2) Since BD bisects <ABC, then m<ABD = m<BDC 5x+5 = 6x-2 -5x 5=x-2 +2 +2 7=x

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