John Casey (mathematician)
John Casey (12 May 1820, Kilbehenny, Ireland – 3 January 1891, Dublin) was a respected Irish geometer. He is most famous for Casey's theorem on a circle that is tangent to four other circles, an extension of the problem of Apollonius. However, he contributed several novel proofs and perspectives on Euclidean geometry. He and Émile Lemoine are considered to be the co-founders of the modern geometry of the circle and the triangle.
He was born in Kilbehenny, Limerick, Ireland and educated locally at Mitchelstown, before becoming a teacher under the Board of National Education. He later became headmaster of the Central Model Schools in Kilkenny City. He subsequently entered Trinity College as a student in 1858, and was awarded the degree of BA in 1862. He was then Mathematics Master at Kingston School (1862-1873), Professor of Higher Mathematics and Mathematical Physics at the newly founded Catholic University of Ireland (1873-1881) and Lecturer in Mathematics at University College, Dublin (1881-1891).
Honours and Awards
In 1869, Casey was awarded the Honorary Degree of Doctor of Laws by Dublin University. He was elected a Fellow of the Royal Society in June, 1875.  He was elected to the Royal Irish Academy and in 1880 became a member of its council. In 1878 the Academy conferred upon him the much coveted Cunningham Gold Medal. His work was also acknowledged by the Norwegian Government, among others. He was elected a member of the Societe Mathematique de France in 1884 and received the honorary degree of Doctor of Laws from the Royal University of Ireland in 1885.
- On Cubic Transformations (Dublin, 1880)
- A Sequel to the First Six Books of the Elements of Euclid (Dublin, 1881)
- The First Six Books of the Elements of Euclid (Dublin, 1882)
- A Treatise on the Analytic Geometry of the Point, Line, Circle and Conic Sections (Dublin, 1885)
- A Treatise on Elementary Trigonometry (Dublin, 1886)
- A Treatise on Plane Trigonometry containing an account of the Hyperbolic Functions (Dublin, 1888)
- A Treatise on Spherical Geometry (Dublin, 1889).
- Irish Monthly (1891), XIX, 106, 152
- Proc. Royal Society (1891), XLIX, 30, p. xxiv.