Results 1 to 2 of 2

Math Help - Circumference to area

  1. #1
    Junior Member
    Joined
    Feb 2007
    Posts
    32

    Circumference to area

    If I know the area of a circle I know that I can find the circumference of the circle by the formula C=Sqrt(4 Pi A) where A is the area of the given circle. My question is where does this formula come from? Thank you.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Oct 2007
    From
    London / Cambridge
    Posts
    591
    Area = \pi r^2 \ \ \ \ \ \ \ \ \ \ \ \ \  \ \ \ \  (1)
     Circumference = 2 \pi r \ \ (2)

    using (1) we have r = \sqrt{\frac{A}{\pi}}

    you put this into the formula for the circumference.

    C = 2\pi \sqrt{\frac{A}{\pi}}

    bring the 2 \pi into the root.


    C = \sqrt{\frac{4\pi^{\not{2}^{~1}} A}{\not{\pi}}}

    cancel down to get C = \sqrt{4 \pi A}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. area and circumference
    Posted in the Geometry Forum
    Replies: 2
    Last Post: May 28th 2010, 06:10 PM
  2. pdf of area and circumference of a circle
    Posted in the Advanced Statistics Forum
    Replies: 6
    Last Post: May 10th 2010, 10:56 PM
  3. Circle area and circumference
    Posted in the Geometry Forum
    Replies: 2
    Last Post: August 30th 2009, 04:19 PM
  4. Diameter, circumference, area
    Posted in the Geometry Forum
    Replies: 1
    Last Post: May 12th 2009, 07:35 AM
  5. Circumference and Area
    Posted in the Geometry Forum
    Replies: 3
    Last Post: March 3rd 2008, 08:30 PM

Search Tags


/mathhelpforum @mathhelpforum