If two complementary Plücker characteristics are equal, then each characteristic is equal to its complement except in four cases where the sum of order and class is 9.
Bioche's Theorem
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References
Coolidge, J. L. A Treatise on Algebraic Plane Curves. New York: Dover, p. 101, 1959.Referenced on Wolfram|Alpha
Bioche's TheoremCite this as:
Weisstein, Eric W. "Bioche's Theorem." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/BiochesTheorem.html