now known in elementary textbooks on differential equations as Clairaut’s equation, and he found the singular solution, but process had been used month, the 1759 return of Halley’s comet.Clairaut had a brother who died when only 16. But who at 14 read a paper on geometry before the French Academy and at 15 published a work on geometry. The father of the Clairaut children was a teacher of mathematics, a correspondent of the Berlin Academy, and a writer on geometry.