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6.8

6.8. Areas of Circles and Sectors. r. Theorem 6.20: Area of a Circle. The area of a circle is p times the square of the radius. 6.8. Areas of Circles and Sectors. Use the formula for area of a circle. Example 1. Find the indicated measure. Area. Solution.

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6.8

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  1. 6.8 Areas of Circles and Sectors r Theorem 6.20: Area of a Circle The area of a circle is p times the square of the radius.

  2. 6.8 Areas of Circles and Sectors Use the formula for area of a circle Example 1 Find the indicated measure. • Area Solution Write formula for area of a circle. Substitute ____ for r. Simplify. Use a calculator.

  3. 6.8 Areas of Circles and Sectors Use the formula for area of a circle Example 1 Find the indicated measure. • Area • Diameter Solution Write formula for area of a circle. Substitute _____ for A. Divide each side by ___. Find the positive sq. rt. of each side. The radius is about ___ inches, so the diameter is about ___ inches

  4. 6.8 Areas of Circles and Sectors A r P B Theorem 6.21: Area of a Sector The ratio of the area of a sector of a circle to the area of the whole circle (pr2) is equal to the ratio of the measure of the intercepted arc to 360o.

  5. 6.8 Areas of Circles and Sectors R P S Q Find areas of sectors Example 2 Find the area of the sector formed by Solution Step 1 Find the measure of the minor and major arcs.

  6. 6.8 Areas of Circles and Sectors R P S Q Find areas of sectors Example 2 Find the area of the sector formed by Solution Step 2 Find the areas of the small and large sectors. Area of small sector =

  7. 6.8 Areas of Circles and Sectors R P S Q Find areas of sectors Example 2 Find the area of the sector formed by Solution Step 2 Find the areas of the small and large sectors. Area of large sector = The areas of the small and large sectors are about _______ square units and _______ square units, respectively.

  8. 6.8 Areas of Circles and Sectors . . . . . A C B Use the Area of a Sector Theorem Example 3 Use the diagram to find the area of Solution Area of sector ACB = The area of is ______ square meters.

  9. 6.8 Areas of Circles and Sectors Checkpoint. Complete the following exercise. • Find the radius of the circle.

  10. 6.8 Areas of Circles and Sectors R P Q S Checkpoint. Complete the following exercise. • Find the areas of the sectors formed by Area of small sector = Area of large sector =

  11. 6.8 Areas of Circles and Sectors . . . . F G H Checkpoint. Complete the following exercise. • Find the area of Area of sector FGH =

  12. 6.7 Circumference and Arc Length Pg. 242, 6.8 #1-22

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