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Arc Length and Sectors of circles

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Arc Length and Sectors of circles Powered By Docstoc
					  STAR REVIEW---DO NOW!
Complete problems:
   ______________________________
           Homework Correction

You know the drill…pass your paper back
to the person sitting directly behind you.
                         Class Exercises
          p. 277 # 7                          p. 291 # 13, 14




            50cm2
7) A = ___________________                    72cm2
                                  13) A = ___________________




                                               24m2
                                  14) A = ___________________
                          Class / Homework
                            p. 278 # 8 - 11


8)            120in2
     A = ___________________




             32cm2
9) A = ____________________




              116cm2
10) A = ____________________




            75in2
11) A = ___________________
Worksheet 9.6
Worksheet 9.6
Worksheet 9.7
Worksheet 9.7
Circle Review Vocabulary (from chapter 2 p. 39)




                        A chord passing through the center
      Circles
                                                       diameter


                                                    center



                                                       radius
      A segment joining the center to any point on the circle
           TODAY…& next class
     Circumference = distance AROUND a circle



          Circles
Area = space INSIDE a circle
               Important Formulas
  C  d                   3.14       or  
                                               22
                                               7
Find the Circumference of this circle
     d=6
    C  6
                                          6
    C = 6(3.14)

      C  18.84 units
Find the Circumference



           C  d
          C  12(3.14)

           C = 37.68 inches
        What if I don’t know the diameter?
Remember, radius =½ diameter or 2radii = diameter
  find the circumference
                           C  2 r
                           C = 2(3.14)(8)
               8 cm

                           C = 50.24 cm
  What about that other value for Pi?
                                            22
find the circumference               or  
                                            7

                         C  d
                             2
                                 22 
          14 in          C  14  
                                 7 

                         C = 44 in
       Class Work – do NOW

 page 283 # 1-7

REMEMBER- “SHOW ME THE WORK”
             is my middle name


 Clever, Mrs. D
            Class / Homework

 Worksheet 9.8

Change in problem # 7:
                22
        use  =
                7
Remember, everyone –SHOW ME the WORK!!!
         MORE Important Formulas

Area of a circle       A r       2

                         3.14
    A   3       2                   3

                              22
                       or  
    A = 3.14(9)               7


    A = 28.26 sq units
                   MORE practice

Area of a circle      A r   2

                     use   3.14
A   9       2

                                        18”
A = 3.14(81)

A = 254.34 sq in                    r=? 9
                       Tricky problem
           Find the area of the shaded region
                                                  A r      2


    1                                         use   3.14
A     (6) 2

    4
                                   6m


 A = (¼) (36)(3.14)
                                  Shaded region = ¼ of the circle
  A = 28.26 sq m
                  Another Tricky problem
              Find the area of the shaded region
                                                    A r     2

                      2
    1 7                                                22
A                                            use  
     3  2                        3½
                                                           7
                  7
      1  22  49 
 A     
      3  7  4                                 1
                                     Shaded region = of the circle
                                                    3
  A = 12.83 sq units
                      Another Tricky problem
                Find the area of the shaded region
                                                         A r         2
     1  22 
A     14 
                 2

     8  7                                                    22
                                                         use  
                                        45
                                       45
                                      14 in                      7
                    28
     1   22   196 
A                                             Shaded region =
     8  7  1 
                                                          45 1
                                                            
                                                         360 8
 A = 77 sq units
                Another Tricky problem
            Find the area of the shaded region
                                                    A r      2


    1
A     (12) 2
                                   60           use   3.14
    6                           12 cm

     1
 A    (3.14)(144)                             Shaded region =
     6                                             60 1
                                                       
  A = 75.36 sq units                                360 6
       What if you can’t use a calculator?

   A=    r2         That means….radius x radius x 3.14



I said….radius times radius times three(3) point one(1) four(4)



Again?….radius times radius times three(3) point one(1) four(4)
          Class Work – do NOW

page 287 find exact area only # 1-5

Remember, show me work!!!
       tonight’s homework

Worksheet 9.9 # 1-13

				
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posted:5/17/2013
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