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B
分析:设等边三角形的边长是a,求出等边三角形的周长,即可求出等边三角形的周率a
1 ;设正方形的边长是x,根据勾股定理求出对角线的长,即可求出周率;设正六边形的边长是b,过F作FQ∥AB交BE于Q,根据等边三角形的性质和平行四边形的性质求出直径,即可求出正六边形的周率a
3 ;求出圆的周长和直径即可求出圆的周率,比较即可得到答案.
设等边三角形的边长是a,则等边三角形的周率a
1 =
![](https://img.yulucn.com/upload/4/93/493b36c6cef6b249a1285726d8f239ed_thumb.jpg)
=3
设正方形的边长是x,由勾股定理得:对角线是
![](https://img.yulucn.com/upload/5/b9/5b9713adba500744ac4d1a7b80a8fd48_thumb.jpg)
x,则正方形的周率是a
2 =
![](https://img.yulucn.com/upload/b/46/b469ed9ceda81575f1c61b8c18df0250_thumb.jpg)
=2
![](https://img.yulucn.com/upload/5/b9/5b9713adba500744ac4d1a7b80a8fd48_thumb.jpg)
≈2.828,
设正六边形的边长是b,过F作FQ∥AB交BE于Q,得到平行四边形ABQF和等边三角形EFQ,直径是b+b=2b,
∴正六边形的周率是a
3 =
![](https://img.yulucn.com/upload/d/98/d98ad450cf420ff4d502567053dd93e5_thumb.jpg)
=3,
圆的周率是a
4 =
![](https://img.yulucn.com/upload/4/55/45514794696154851a941e965e8de910_thumb.jpg)
=π,
∴a
4 >a
3 >a
2 .
故选B.
1年前
3