求出下图中阴影部分的周长和面积.
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求出下图中阴影部分的周长和面积.
![](http://img.wesiedu.com/upload/5/f3/5f3fbe561ca548c372561389b942bcbc.jpg)
![](http://img.wesiedu.com/upload/5/f3/5f3fbe561ca548c372561389b942bcbc.jpg)
![求出下图中阴影部分的周长和面积.](/uploads/image/z/8621809-25-9.jpg?t=%E6%B1%82%E5%87%BA%E4%B8%8B%E5%9B%BE%E4%B8%AD%E9%98%B4%E5%BD%B1%E9%83%A8%E5%88%86%E7%9A%84%E5%91%A8%E9%95%BF%E5%92%8C%E9%9D%A2%E7%A7%AF.)
周长=1/4π×2r+1/4π×2R+1+1=1/4×3.14×2×2+1/4×3.14×2×(2+1)+1+1
=1/4×3.14×2(2+2+1)+1+1
=7.85+1+1=9.85dm
面积=1/4π R∧2-1/4 r∧2
=1/4π(R∧2- r∧2)
=1/4π×(3×3- 2×2)
=3.925 dm2
=1/4×3.14×2(2+2+1)+1+1
=7.85+1+1=9.85dm
面积=1/4π R∧2-1/4 r∧2
=1/4π(R∧2- r∧2)
=1/4π×(3×3- 2×2)
=3.925 dm2