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圆周率计算公式

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设把圆无限等分,那么如图AB=2∏r/∞(r为半径)
∵OB=OA=r
∴ΔOBA为等腰三角形
作OG⊥AB
∴AG=GB=AB/2=(2∏r/∞)/2=∏r/∞
∵Sin∠AOG=AG/AO
∵∠AOG=(∠AOB)/2=(360/∞)/2=180/∞
∴Sin(180/∞)=AG/AO
又∵AO=r ∴Sin(180/∞)=AG/r
∵AG=∏r/∞
∴(∏r/∞)/r= Sin(180/∞)
∴∏/∞= Sin(180/∞)
∴∏= Sin(180/∞)* ∞

One Comment

  1. June 8, 2009 at 7:22 pm

    o_o好麻烦哦!!!!

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