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Homework Help: Circle problem

  1. Oct 20, 2013 #1
    1. The problem statement, all variables and given/known data
    Find the length of the chord which the circle 3x^2+3y^2-29x-19y+56=0 cuts off from the straight line x-y+2+=0. Find the equation of the circle with this chord as diameter

    2. Relevant equations

    3. The attempt at a solution
    I can solve the second part of the question very easily. What I am really finding difficult is trying to construct a method of calculating the length of the chord. Is there any formula or equation for it????
  2. jcsd
  3. Oct 20, 2013 #2
    Think about it. If you were dealing with simple geometry where you were given the radius of circle and the distance of chord from the centre, how do you find the length of chord?
  4. Oct 21, 2013 #3


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    With the information given, it might be easier just to find the intercepts.
  5. Oct 22, 2013 #4
    @haruspex I don't precisely get what you are trying to put across. Are you suggesting that I should find the intercepts of the straight line as well as the radius of the circle from the given two equations. Tell me how the intercepts of the straight line relate with the radius of the circle??
  6. Oct 22, 2013 #5
    @Pranav Arora But the distance of chord from the centre is not given..
  7. Oct 22, 2013 #6
    You can find it...You have the equation of chord and coordinate of center.
  8. Oct 22, 2013 #7
    Dumbledore211...Simply find the points of intersection of the circle with the straight line .This will give you two points in the plane .In the first part you have to find the length of the chord which is nothing but the distance between these two points .
  9. Oct 22, 2013 #8
    If you have the intercepts you can use it to find the position of center of the new circle. ED- And the length as Tanya pointed out above(crossed posts)
  10. Oct 22, 2013 #9
    Thank you, Tanya Sharma. I finally got the answer which is 4(2)^1/2
  11. Oct 22, 2013 #10
    Well done...
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