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Math Help - equation

  1. #1
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    equation

    this is an equation... (x^2)/3 + (y^2)/5 = 15. this is an ellipse but how to calculate semi major axis from it?
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  2. #2
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    Write the equation of ellipse in the standard form.

    \frac{x^2}{45} + \frac{y^2}{75} = 1

    Now can you find the semi-major axis?
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  3. #3
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    check

    it comes out to be (5*3^(1/2))/2. am i right?
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  4. #4
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    Yes. You are right.
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  5. #5
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    Quote Originally Posted by vyomictor View Post
    it comes out to be (5*3^(1/2))/2. am i right?
    No, you are not right. The semi-major axis is \sqrt{75} = 5 \sqrt{3}.

    If you have the ellipse \displaystyle \frac{x^2}{a^2} + \frac{y^2}{b^2} then the semi-major axis is either a (if a > b) or b (if b > a).
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