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1.6 Measuring Angles

1.6 Measuring Angles. What you'll learn today. To measure angles using a protractor. To draw angles using a protractor. Different types of angles. P. 75 °. Q. R. In geometry, angles are measured in units called _______. degrees. The symbol for degree is °.

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1.6 Measuring Angles

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  1. 1.6 Measuring Angles

  2. What you'll learn today. To measure angles using a protractor. To draw angles using a protractor. Different types of angles

  3. P 75° Q R In geometry, angles are measured in units called _______. degrees The symbol for degree is °. In the figure below, the angle is 75 degrees.

  4. Now, let’s measure an angle using a protractor. Use a protractor to measure SRQ. 1) Place the center point of the protractor on vertex R. Align the straightedge with side RS. 2) Use the scale that begins with 0 at RS. Read where the other side of the angle, RQ, crosses this scale. Q R S 1200

  5. Let’s measure the following angles. m SRQ = m SRJ = m SRG = H J G Q S R Find the measurement of: 180 45 150

  6. Let’s measure an angles m QRG = m GRJ = m SRH H J G Q S R 70 180 – 150 = 30 150 – 45 = 105

  7. Try this one. 1) Draw AB 3) Locate and draw point C at the mark labeled 135. Draw AC. C A B Use a protractor to draw an angle having a measure of 135. 2) Place the center point of the protractor on A. Align the mark labeled 0 with the ray.

  8. Lets look at some angles. right angle: 900 acute angle: less than 900 obtuse angle: more than 900 straight angle: 1800

  9. 40° 110° 90° 50° 75° 130° Classify each angle as acute, obtuse, or right. Acute Obtuse Right Obtuse Acute Acute

  10. Let’s use Algebra to answer the following. The measure of B is 138.Solve for x. 5x - 7 B B = 5x – 7 and B = 138 Given: (What do you know?) 5x – 7 = 138 Check! 5x = 145 5(29) -7 = ? x = 29 145 -7 = ? 138 = 138

  11. Here’s another one. The measure of H is 67.Solve for y. H 9y + 4 H = 9y + 4 and H = 67 Given: (What do you know?) 9y + 4 = 67 Check! 9y = 63 9(7) + 4 = ? y = 7 63 + 4 = ? 67 = 67

  12. Is m a larger than m b ? 60° 60°

  13. R X 2) Draw and label a point X in the interior of the angle. Then draw SX. S T Let’s try something different. 1) Draw an acute, an obtuse, or a right angle. Label the angle RST. 45° 75° 30° 3) For each angle, find mRSX, mXST, and RST.

  14. Here are some more types of angles. congruent angles: vertical angles: opposite angles adjacent angles:

  15. Here are some questions. B 2 1 1 2 G N L 1 J 2 Determine whether 1 and 2 are adjacent angles. No. They have a common vertex B, but _____________ no common side Yes. They have the same vertex G and a common side with no interior points in common. No. They do not have a common vertex or ____________ a common side The side of 1 is ____ The side of 2 is ____

  16. Let’s try something different. 1 2 1 2 Z D X Determine whether 1 and 2 are adjacent angles. No. Yes. In this example, the noncommon sides of the adjacent angles form a ___________. straight line linear pair These angles are called a _________

  17. 130° x° Let’s try something different. Find the value of x in the figure: The angles are vertical angles. So, the value of x is 130°.

  18. Let’s try something different. Find the value of x in the figure: (x – 10)° 125° The angles are vertical angles. (x – 10) = 125. x – 10 = 125. x = 135.

  19. Assignment Pre AP Geometry (Textbook) 1.6: Page ; Problems #2-44 Even Geometry (Workbook) 1.6: Page 259; Problems #1-15 All

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