Also known as the first fundamental form,
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In the principal axis frame for three dimensions,
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At ordinary points on a surface, the line element is positive definite.
Line Element
See also
Area Element, Fundamental Forms, Minkowski Metric, Volume ElementExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Line Element." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/LineElement.html