SECANT, in trigonometry, denotes a right line drawn from the centre of a circle, which, cutting the circumference, proceeds till it meets with a tangent to the same circle. See GEOMETRY, n° 24—28. Line of SECANTS, one of those lines or scales which are usually put upon sectors. How such a scale is formed will be seen by a bare inspection of fig. 53. Plate CCXV.; for C 10, C 20, C 30, &c. drawn from the centre C to the line of tangents BE, being the real secants of the arches B 10, B 20, B 30, it is obvious that by marking off the distances B 10, B 20, B 30, upon any other line, we make that line a scale of secants. Seceders.