a. Geom. [f. TRI- + L. līneāris LINEAR, f. līnea line.] Of, contained by, or having some relation to, three lines (including curved as well as straight lines).
Trilinear co-ordinates, a system of co-ordinates determining a point in a plane by its distances, measured in three fixed directions, from three fixed straight lines forming a triangle.
1715. trans. Gregory’s Astron., III. (1726), I. 379. The trilinear Figure ALS is to the whole Ellipse, as the trilinear Figure AGS to the whole Circle.
1807. Hutton, Course Math., II. 115. The Sector or Trilinear Space contained by an Arc of the Curve and two Radii.
1896. Yale Univ. Grad. Course Instr., 70. A course in analytical geometry…. It includes the use of determinants and trilinear coördinates.
