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Measuring Angles

Measuring Angles. Lesson 1.3. Big angle vs. Little angle. Definition of degree. Degrees were developed by the Babylonians thousands of years ago. They divided a circle into 360 parts and called each part one degree. Notation for angle measurement.

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Measuring Angles

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  1. Measuring Angles Lesson 1.3

  2. Big angle vs. Little angle

  3. Definition of degree Degrees were developed by the Babylonians thousands of years ago. They divided a circle into 360 parts and called each part one degree.

  4. Notation for angle measurement The symbol for degrees, as you probably already know, is a small superscript circle. 45° 112° 37°

  5. Classification of Angles • Acute Angles • Right Angles • Obtuse Angles • Straight Angles

  6. Definition • Acute angles angles that measure less than 90°

  7. Definition • Right angles angles that measure 90° Symbol for right angles

  8. Definition • Obtuse angles angles that measure more than 90° but less than 180°

  9. Definition • Straight angle an angle that makes a straight line and measure 180°

  10. What is a protractor?

  11. Measuring an angle

  12. Measuring an angle

  13. Measuring an angle

  14. Angle congruence Angles are congruent if they have the same measure 48° A 48° B

  15. Angle congruence Angles are congruent if one can be moved onto the other so that they match exactly.

  16. Marking Congruent Angles and Sides with Tick Marks. A D B C E F AB DE A D BC EF B E C F AC DF

  17. Pairs of Angles • Complementary Angles • Supplementary Angles • Linear Pair

  18. Definition • Complementary angles Two angles that total 90 degrees 30 and 60 27 and 63 12 and 78

  19. Definition • Supplementary angles Two angles that total 180 degrees • and 155 • 67 and 113 • 124 and 56

  20. SOL Practice 1

  21. Definition • Linear angles Two angles that share a side and make a line. Linear angles total 180° Similar to Supplementary

  22. SOL Practice 2

  23. Angle addition postulate If point S is in the interior (middle) of angle PQR, then the measure of PQS + measure of SQR = measure of PQR S P Q R

  24. Angle addition postulate • Practice Problems • Page 32 # 36-44

  25. Assignment • A4 • Worksheet 1.3 • pp. 30-32 # 13, 27-44

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