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Sketch the graph of 4x^2 + 9y^2 = 144. Is this an ellipse?

  • Thread starter kasse
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  • #1
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I'm going to sketch the graph of the eq. 4x^2 + 9y^2 = 144

This is an ellipse with its center at the origo and major semiaxis 6 and minor semiaxis 4. But how do I find the foci?
 

Answers and Replies

  • #2
682
1
[tex]a^2=b^2+c^2[/tex]
where c is the focal length.

the equation comes directly from one definition of ellipse:
the sum of distance between any point on the ellipse and the foci = 2a.
 
  • #3
366
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Ah, makes sense. Thank you!
 

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