major axis
geometry
Quick Summary
The major axis is a key geometric feature of an ellipse. It is defined as the longest diameter of the ellipse, passing through both foci and extending to the curve's edges. This line is perpendicular to the minor axis, which is the shortest diameter and also passes through the ellipse's center. The length of the major axis is often denoted as 2a in mathematical equations for an ellipse. The semimajor axis is simply half the length of the major axis. Ellipses are symmetrical about both their major and minor axes.123
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