Charles-Julien Brianchon

December 19, 1783 (age 80)

Sevres, Hauts-de-Seine, France

After graduation, Charles-Julien Brianchon became a lieutenant in artillery in the armies of Napoleon. He took part in the Peninsular campaigns, serving in Spain and Portugal, and is said to have distinguished himself both in bravery and ability. The rigors of his army service affected his health, and after the cessation of hostilities in 1813, Brianchon applied for a teaching position. He was finally appointed professor at the Artillery School of the Royal Guard in 1818. By this time he had published several works in geometry, including "Sur les surfaces courbes du second degré" (1816), "Mémoire sur les lignes du second ordre" (1817), 'Application de la théorie des transversales" (1818), and "Solution de plusieurs problèmes de géométrie" (1818). Brianchon’s teaching duties apparently affected both his output and his interests. In 1820 there appeared "Recherches sur la détermination d’une hyperbole équilatère, au moyen de quatres conditions données," written with Poncelet. It is notable for containing the nine-point circle theorem and is an instance of the many times this theorem has been rediscovered by independent investigators. At any rate, this paper contains the first complete proof of the theorem and the first use of the term "nine-point circle." Brianchon’s next publication, "Description du laboratoire de chimie de l’École d’Artillerie de la Garde Royale" (1822), indicates his change of interests. Two works appeared in 1823: "Des courbes de raccordement" and "Mémoire sur la poudre à tirer". His last known work, "Essai chimique sur les réactions foudroyantes", appeared in 1825. Brianchon ceased writing after 1825 and devoted all his time to teaching.

Charles-Julien Brianchon

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chemist mathematician scientist

Background

Charles-Julien Brianchon was born on December 19, 1783, in Sèvres, Hauts-de-Seine, France.

Education

Brianchon entered the École Polytechnique in 1804 and was a pupil of the noted geometer Gaspard Monge. While a student there, he published his first paper, "Sur les surfaces courbes du second degré" (1806), which contained the famous theorem named after him. He graduated first in his class in 1808.

Career

After graduation, Charles-Julien Brianchon became a lieutenant in artillery in the armies of Napoleon. He took part in the Peninsular campaigns, serving in Spain and Portugal, and is said to have distinguished himself both in bravery and ability. The rigors of his army service affected his health, and after the cessation of hostilities in 1813, Brianchon applied for a teaching position. He was finally appointed professor at the Artillery School of the Royal Guard in 1818.

By this time he had published several works in geometry, including "Sur les surfaces courbes du second degré" (1816), "Mémoire sur les lignes du second ordre" (1817), 'Application de la théorie des transversales" (1818), and "Solution de plusieurs problèmes de géométrie" (1818).

Brianchon’s teaching duties apparently affected both his output and his interests. In 1820 there appeared "Recherches sur la détermination d’une hyperbole équilatère, au moyen de quatres conditions données," written with Poncelet. It is notable for containing the nine-point circle theorem and is an instance of the many times this theorem has been rediscovered by independent investigators. At any rate, this paper contains the first complete proof of the theorem and the first use of the term "nine-point circle."

Brianchon’s next publication, "Description du laboratoire de chimie de l’École d’Artillerie de la Garde Royale" (1822), indicates his change of interests. Two works appeared in 1823: "Des courbes de raccordement" and "Mémoire sur la poudre à tirer". His last known work, "Essai chimique sur les réactions foudroyantes", appeared in 1825. Brianchon ceased writing after 1825 and devoted all his time to teaching.

Achievements

Charles-Julien Brianchon is remembered as a mathematician, who derived a geometrical theorem (now known as Brianchon’s theorem) useful in the study of the properties of conic sections (circles, ellipses, parabolas, and hyperbolas) and who was innovative in applying the principle of duality to geometry.

Works

$M\u00E9moire Sur Les Lignes Du Second Ordre: Faisant Suite Aux Recherches Publi\u00E9es Dans Les Journaux De L\'\u00E9cole Royale Polytechnique M\u00E9moire Sur Les Lignes Du Second Ordre: Faisant Suite Aux Recherches Publi\u00E9es Dans Les Journaux De L\'\u00E9cole Royale Polytechnique$ $Application de la th\u00E9orie des transversales, cours d\'operations g\u00E9om\u00E9triques sur le terrain, fait a l\'\u00E9cole d\'artillerie Application de la th\u00E9orie des transversales, cours d\'operations g\u00E9om\u00E9triques sur le terrain, fait a l\'\u00E9cole d\'artillerie$

book
- Mémoire Sur Les Lignes Du Second Ordre: Faisant Suite Aux Recherches Publiées Dans Les Journaux De L'école Royale Polytechnique 1817
- Application de la théorie des transversales, cours d'operations géométriques sur le terrain, fait a l'école d'artillerie 1818

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book

Mémoire Sur Les Lignes Du Second Ordre: Faisant Suite Aux Recherches Publiées Dans Les Journaux De L'école Royale Polytechnique

Application de la théorie des transversales, cours d'operations géométriques sur le terrain, fait a l'école d'artillerie

Charles-Julien Brianchon

Background

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Career

Achievements

Works

book

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Education

1804 - 1808

Career

1818

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