Definition:Ellipse/Major Axis
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Definition
Consider an ellipse $K$ whose foci are $F_1$ and $F_2$.
The major axis of $K$ is the line segment passing through both $F_1$ and $F_2$ whose endpoints are where it intersects $K$.
In the above diagram, $V_1 V_2$ is the major axis of $K$.
Semi-Major Axis
A semi-major axis of $K$ is either half of the major axis of $K$ from its midpoint to its endpoint.
Also see
Sources
- 1933: D.M.Y. Sommerville: Analytical Conics (3rd ed.) ... (previous) ... (next): Chapter $\text {IV}$. The Ellipse: $2$. To find the equation of the ellipse in its simplest form
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): major axis
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): major axis
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): major axis