Trigonometrical lines

lines which are employed in solving the different cases of plane and spherical trigonometry, as sines, tangents, secants, and the like. These lines, or the lengths of them, are trigonometrical functions of the arcs and angles to which they belong.

See also: Trigonometric

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.