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Henri Brocard was a French army officer who studied meteorology but is best remembered for his work on the triangle. The Brocard points of a triangle ABC are O, O' where OAB, OBC and OCA and the angles O'BA, O'CB and O'AC are equal. [Draw a circle tangent to AB at A passing through C; another tangent to BC at B passing through A; a third tangent to CA at C passing through B. They are concurrent at O.] Angle OAB is called the Brocard angle and satisfies cot OAB = cot A + cot B + cot C.
References (2 books/articles)