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I wonder when was discovered the nine point conic. English Wikipedia article about it https://en.wikipedia.org/wiki/Nine-point_conic is misleading. The nine point conic wasn't discovered in 1892.

In the book Trilinear Coordinates, by William Allen Whitworth, published in 1866(https://ia801405.us.archive.org/21/items/trilinearcoordin029731mbp/trilinearcoordin029731mbp.pdf) one can see that the proof of the existence of the nine point conic is proposed as an exercise (page 473, exercises 438 and 439).

My rough guess is that the nine point conic was discovered in the very beginning of the nineteen century.

Any ideas?

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    $\begingroup$ Well, Feuerbach described the nine-point circle only in 1822, but he was only aware of six points, and Terquem described the remaining three soon after. After that anybody with some knowledge of projective geometry would have been aware of the nine-point conic. I am guessing Bôcher was first to go into details of it. $\endgroup$ – Conifold Sep 21 '18 at 0:11

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