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Homework Help: Is it possible to work out the centre of an ellipse?

  1. Oct 31, 2005 #1
    Is it possible to work out the centre of an ellipse?
    The question asks for the eccentric angle of the ellipse with the equation x²+9y²=13 at point (2,1)....
    I have no idea how to get this, I know that the angle would be arctan(1/2) if the ellipse was centred at (0,0)

  2. jcsd
  3. Oct 31, 2005 #2
    But the ellipse IS centered at the origin. It asks for the eccentric angle between the x-axis and the line joining (0,0) and (2,1).

    edit: PS: The eccentric angle is not simply arctan(y/x), you have to take the axes of the ellipse into account too!

    - Kamataat
    Last edited: Oct 31, 2005
  4. Oct 31, 2005 #3
    I am somewhat confused. Surely the line joining (0,0) and (2,1) makes arctan (.5) of an angle with the x axis.:confused:
  5. Nov 1, 2005 #4
  6. Nov 1, 2005 #5
    Thanks a lot :biggrin:
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