Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Finding the area of a circle using integration

  1. May 7, 2010 #1
    Let's say I have the equation for a circle but don't know how to calculate its radius. How could I use integration to find its area?
  2. jcsd
  3. May 7, 2010 #2
    You can always get the radius from circle equations !!

    However, all circle equations are integrated by trigonometric substitution
    and it can also be done by integration by parts but that is a bit tricky!!
  4. May 7, 2010 #3

    jack action

    User Avatar
    Science Advisor
    Gold Member

    The area of a circle is a equal to the area of two half-circle.

    The equation of a half-circle (assuming (y-b) is always positive and that you don't understand that r is the radius):


    So the area of a circle is equal to: [tex]2\int_{-r-a}^{r-a}y_{(x)}dx[/tex]

    That's a complicated way, but I guess it can be done.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook