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How do I calculate the length of the major axis of an ellipse? I have the eccentricity and the length of the semi-major axis.

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    You multiply the length of the semi-major axis by 2. You don't need the eccentricity. The semi-major axis is half the major axis by definition.2012-05-08

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As wikipedia points out, the eccentricity $\epsilon$ of an ellipse obeys the equation $\epsilon=\sqrt{1-\left(\frac{b}{a}\right)^2}$ where $a$ and $b$ are respectively the semi-major and semi-minor axes of the ellipse.

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    @Ron: sounds like an answer to me...2012-05-08
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Multiply the semi-major axis by 2, and that's the major axis.