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briana.img

  • one year ago

What are the foci of the following graph?

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  1. briana.img
    • one year ago
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  2. briana.img
    • one year ago
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    I started with a=1 and b=2 and so c^2=1^2-2^2 it ends up to be c^2=-3 but i don't feel as that's right

  3. Loser66
    • one year ago
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    Look at the graph, we can see that the foci must be on the x-axis, hence, the coordinate must be under the form of (-x,0) and (x,0). Therefore, we can get rid of A and D

  4. Loser66
    • one year ago
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    Now, if it is B, the point \((1+\sqrt 3,0)\) has x-coordinate >1, that is it is out of the graph --> cannot be a foci. Now, we have just.......??

  5. briana.img
    • one year ago
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    @Loser66 just C left

  6. Loser66
    • one year ago
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    Yup, but does it make sense to you?

  7. briana.img
    • one year ago
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    @Loser66 yeah i'll look at this next time i'm having trouble

  8. dan815
    • one year ago
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    do you know what is special about the foci

  9. Loser66
    • one year ago
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    @dan815 Yes, I do. However, in this case, it is easier than the traditional way on finding the foci out by rejecting the wrong one.

  10. dan815
    • one year ago
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    |dw:1435322594474:dw|

  11. dan815
    • one year ago
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    |dw:1435322627563:dw|

  12. dan815
    • one year ago
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    if you draw a straight line from one foci to another foci while hitting the ellipse anywhere once, the length of the lines forces is constant, using that we can figure out where a foci is for any ellipsode with a and b, dominant and codominant axis respectively

  13. dan815
    • one year ago
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    |dw:1435322824510:dw|

  14. dan815
    • one year ago
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    |dw:1435322927884:dw|

  15. dan815
    • one year ago
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    |dw:1435322980864:dw|

  16. dan815
    • one year ago
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    |dw:1435323122841:dw|

  17. dan815
    • one year ago
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    |dw:1435323133713:dw|

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