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California Standards

California Standards. Preparation for MG2.1 Identify angles as vertical, adjacent, complementary, or supplementary and provide descriptions of these terms. Also covered: Prep for MG2.3. Vocabulary. angle vertex acute angle right angle obtuse angle straight angle.

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California Standards

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  1. California Standards Preparation for MG2.1 Identify angles as vertical, adjacent, complementary, or supplementary and provide descriptions of these terms. Also covered: Prep for MG2.3

  2. Vocabulary angle vertex acute angle right angle obtuse angle straight angle

  3. An angle is formed by two rays with a common endpoint, called the vertex. An angle can be named by its vertex or by its vertex and a point from each ray. The middle point in the name should always be the vertex. Angles are measured in degrees. Use the symbol °to show degrees.

  4. F H G Additional Example 1: Measuring an Angle with a Protractor Use a protractor to measure the angle. • Place the center point of the protractor on the vertex of the angle.

  5. F H G Additional Example 1 Continued Use a protractor to measure the angle. • Place the protractor so that ray GH passes through the 0° mark.

  6. F H G Additional Example 1 Continued Use a protractor to measure the angle. • Using the scale that starts with 0° along ray GH, read the measure where ray GF crosses.

  7. Reading Math mFGH is read “the measure of angle FGH.”

  8. F H G Additional Example 1 Continued Use a protractor to measure the angle. • The measure of FGH is 120°. Write this as mFGH = 120°.

  9. Check It Out! Example 1 Use a protractor to measure the angle. G I H • Place the center point of the protractor on the vertex of the angle.

  10. Check It Out! Example 1 Continued Use a protractor to measure the angle. G I H • Place the protractor so that ray HI passes through the 0° mark.

  11. Check It Out! Example 1 Continued Use a protractor to measure the angle. G I H • Using the scale that starts with 0° along ray HI, read the measure where ray HG crosses.

  12. Check It Out! Example 1 Continued Use a protractor to measure the angle. G I H • The measure of GHI is 70°. Write this as mGHI = 70°.

  13. Additional Example 2: Drawing an Angle with a Protractor Use a protractor to draw an angle that measures 80°. • Draw a ray on a sheet of paper.

  14. Additional Example 2 Continued Use a protractor to draw an angle that measures 80°. • Place the center point of the protractor on the endpoint of the ray. • Place the protractor so that the ray passes through the 0° mark.

  15. Additional Example 2 Continued Use a protractor to draw an angle that measures 80°. • Make a mark at 80° above the scale on the protractor. • Use a straightedge to draw a ray from the endpoint of the first ray through the mark you made at 80°.

  16. Check It Out! Example 2 Use a protractor to draw an angle that measures 45°. • Draw a ray on a sheet of paper.

  17. Check It Out! Example 2 Continued Use a protractor to draw an angle that measures 45°. • Place the center point of the protractor on the endpoint of the ray. • Place the protractor so that the ray passes through the 0° mark.

  18. Check It Out! Example 2 Continued Use a protractor to draw an angle that measures 45°. • Make a mark at 45° above the scale on the protractor. • Use a straightedge to draw a ray from the endpoint of the first ray through the mark you made at 45°.

  19. Reading Math Right angles are usually marked with a symbol. An acute angle measures less than 90°. A right angle measures exactly 90°.

  20. An obtuse angle measures more than 90° and less than 180°. A straight angle measures exactly 180°.

  21. Additional Example 3: Classifying Angles Classify each angle as acute, right, obtuse, or straight. A. B. The angle measures exactly 90°, so it is a right angle. The angle measures less than 90°, so it is an acute angle.

  22. Check It Out! Example 3 Classify each angle as acute, right, obtuse, or straight. A. B. The angle measures exactly 180°, so it is a straight angle. The angle measures less than 90°, so it is an acute angle.

  23. Additional Example 4: Application A welder used this piece of metal on his project. Classify X, Y, and Z. X right The angle is marked as a right angle. Y obtuse The angle measures more than 90° and less than 180°. Z acute The angle measures less than 90°.

  24. Check It Out! Example 4 A metal jeweler used this piece of metal on her project. Classify A, B, and D. A D B C A obtuse The angle measures more than 90° and less than 180°. The angle measures less than 90°. B acute D right The angle is marked as a right angle.

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