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#1 Re: Help Me ! » Area of a circle » 2006-09-23 04:32:18

irspow wrote:

Integrating a line equation gives the area below the curve (or line).  The equation for the first quadrant is:
     y = √r²-x²

  Integrating this equation from zero to r gives:

     x/2 (√r²-x²) + r²/2 (arcsin x/r) = πr²/4

  Since this is only the area of one quadrant, you must multiply this by 4 which gives π

Hi guys

Sorry to resurrect this thread but I really need to be able to derive the formula for the area of a circle using integration and I can't find anything useful on the internet. Please could you explain how it works without missing stages out so it's easier to follow. How do you integrate the "r"? I can't remember!

Thank you so much.

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