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Circles & Related Figures AB is a radius AC is a diameter EF is a cord ∠DBC is a center angle A E C 0 10 20 30 40 50 60 70 80 90 100 110 120 130 14 0 15 0 16 0 17 0 18 0 18 0 17 0 16 0 15 0 14 0 13 0 120 110 100 90 80 70 60 50 40 30 20 10 0 Lines Angles Measuring Angles Drawing Angles right angle straight angle acute angle obtuse angle right angle A D G H E F I An angle is made up of two rays that share the same endpoint called the vertex. A straight angle forms a straight line. A right angle forms a square corner. Place the center point of the protractor over the vertex (corner) of the angle. Draw the ray DF. Place the center point of the protractor on the end point of the ray. Line up the ray DF so that it passes through the 0º mark of the protractor. Make a mark at 115º and label it E. Draw ray DE from the end point of ray DF to the mark you made at 115º. Place the protractor so that ray AC is over the base line of the protractor and passes through the 0º mark. Read the measure where the other ray AB crosses the protractor. An acute angle is less than a right angle. An obtuse angle is greater than a right angle. A ray is part of a line with one endpoint and goes on forever in the other direction. A line segment is part of a line between two endpoints. A line is a straight collection of points that extend in two opposite directions without end. A point is a location in space. AB CD BAC • point A • point B AB CD AB CD A A B D C B C interior exterior side A B D A B C D E F A B D C Line Segment Line Ray Angle Point Measure ∠BAC Draw ∠EDF of 115º B D F center The measure of ∠BAC is 65º Step 1 Step 2 Step 3 Step 1 Step 2 Step 3 Step 4 Step 5 0 10 20 30 40 50 60 70 80 90 100 110 120 130 14 0 15 0 16 0 17 0 18 0 18 0 17 0 16 0 15 0 14 0 13 0 120 110 100 90 80 70 60 50 40 30 20 10 0 A center point B C © Copyright NewPath Learning. All Rights Reserved. 93-4510 www.newpathlearning.com Lines, Angles & Circles

\|xiBAHBDy01650sz\ Circles & Related Figures AB is a AC is a EF is a ∠DBC is a A E C 0 10 20 30 40 50 60 70 80 90 100 110 120 130 14 0 15 0 16 0 17 0 18 0 18 0 17 0 16 0 15 0 14 0 13 0 120 110 100 90 80 70 60 50 40 30 20 10 0 Lines Angles Measuring Angles Drawing Angles A D G H E F I Define: Example: Define: Example: Define: Example: Define: Example: Define: Example: Place the center point of the protractor over the vertex (corner) of the angle. Place the protractor so that ray AC is over the base line of the protractor and passes through the 0º mark. Read the measure where the other ray AB crosses the protractor. Line Segment Line Ray Angle Point Measure ∠BAC Draw ∠EDF of 115º B D F center The measure of ∠BAC is 65º Step 1 Step 2 Step 3 Step 1 Step 2 Step 3 Step 4 Step 5 Key Vocabulary Terms • acute angle • angle • circle • cord • diameter • line • line segment • obtuse angle • point • protractor • radius • ray • right angle • straight angle • straight line • vertex 0 10 20 30 40 50 60 70 80 90 100 110 120 130 14 0 15 0 16 0 17 0 18 0 18 0 17 0 16 0 15 0 14 0 13 0 120 110 100 90 80 70 60 50 40 30 20 10 0 A center point B C © Copyright NewPath Learning. All Rights Reserved. 93-4510 www.newpathlearning.com Lines, Angles & Circles