If each of two nonparallel transversals with nonminimal directions meets a given curve in finite points only, then the ratio of products of the distances from the two sets of intersections to the intersection of the lines is independent of the position of the latter point.
Newton's Theorem
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References
Coolidge, J. L. A Treatise on Algebraic Plane Curves. New York: Dover, p. 189, 1959.Referenced on Wolfram|Alpha
Newton's TheoremCite this as:
Weisstein, Eric W. "Newton's Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/NewtonsTheorem.html