Morley's trisector theorem

Etymology
Named for Anglo-American mathematician, who discovered it in 1899.

Proper noun

 * 1)  A theorem stating that in any triangle, the three points of intersection of the adjacent angle trisectors form an equilateral triangle.
 * 2) * 1996, Dongming Wang, GEOTHER: A Geometry Theorem Prover, M. A. McRobbie, J. K. Slaney (editors), Automated Deduction - Cade-13: 13th International Conference, Proceedings, Springer, 1104, page 166,
 * The provers are practically efficient: a number of difficult theorems including Morley's trisector theorem, Thebault's recently confirmed conjecture and MacLane's non-existence of real 83 configuration have been proved by them in the matter of seconds.
 * The provers are practically efficient: a number of difficult theorems including Morley's trisector theorem, Thebault's recently confirmed conjecture and MacLane's non-existence of real 83 configuration have been proved by them in the matter of seconds.

Translations

 * French: théorème de Morley
 * Italian: teorema di Morley