who discovered the orthocenter of a triangle? I tried to answer Is there a name for this result in planar geometry? and wanted to go back to the first mention of the orthocenter (or even the altitude of a triangle, but i did draw a complete blank. Orthocenter or even altitude is not mentioned in Euclid's elements (Heath's translation) it is also not mentioned in Heath, T.L. (1921). A History of Greek Mathematics: From Thales to Euclid I. Oxford. < So when was it discovered? (please add references)

`The three altitudes of any triangle are concurrent at the orthocenter H (Durell 1928). This fundamental fact did not appear anywhere in Euclid's Elements.`

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`The name was invented by Besant and Ferrers in 1865 while walking on a road leading out of Cambridge, England in the direction of London (Satterly 1962).`

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