triangular scale

A scale used by draughtsmen and engineers for laying down measurements on paper. Each edge is differently divided, giving a variety of scales to select from. The rule being laid flat on the paper, the distances required to be laid down can at once be pricked off, dispensing with the use of dividers. They are commonly made (1) Arithmetical triangle : A name given to a table of numbers arranged in a triangular manner, and formerly employed in arithmetical computation. It 1 is equivalent to a multi plica- 1 1 tion table. The first vertical 12 1 column consisted of units; 133 1 the second of a series of nat- 1 4 6 4 1 ural numbers; the third of 1 5 10 10 5 1 triangular numbers; the 16 15 20 15 6 1 of boxwood, but sometimes of metal-silver, or fourth of pyramidal numbers, Arithmetical Triand so on. [FIGURATE-NUMangle. IMG:content-1411.png:[blocks in formation] andros a male.] tri-an-dri-a, s . pl . [Pref. tri- , and Greek aner , Botany: The third cla of Linnæus' Artificial System, consisting of plants with three stamens. Orders: Monogynia, Digynia, and Trigynia. tri-ăn-dri-an, tri-ăn-drous, a . [TRI AND RIA.] Botany : Pertaining or belonging to the Linnæan cla Tri and ria; having three distinct and equal stamens in the same flower with a pistil or pistils. tri-ăn-gle, tri-ăn-gle, *try-an-gle, s. [Fr. triangle, from Lat. triangulum , neut. of triangulus =having three angles: tri a =three, and angulus an angle; Sp. & Port. triangulo ; Ital. triangolo .] I. Ord. Lang.: A three-cornered figure, plot of ground, or the like. [II. 5.] IMG:content-1412.png:[blocks in formation] 3. Draughtsmanship: A three-cornered straightedge, used in conjunction with the T-square for drawing parallel, perpendicular, or diagonal lines. It has one right angle, the two others being each of 45°, or one of 30° and the other of 60°. 4. Eccles. Art : A symbol of the Holy Trinity represented by an equilateral triangle. [TRINITY.] 5. Geom.: A portion of a surface bounded by three lines, and consequently having three angles. Tri. angles are either plane, spherical, or curvilinear. A plane triangle is a portion of a plane bounded by three straight lines called sides, and their points of intersection are the vertices of the triangle. Plane triangles may be cla ified either with reference to their sides or their angles. When cla ified with reference to their sides, there are two cla es: (1) Scalene triangles, which have no two sides equal; (2) Isosceles triangles, which have two sides equal, The isosceles triangle has a particular case, called the equilateral triangle, all of whose sides are equal. When cla ified with reference to their angles, there are two cla es: (1) Right-angled triangles, which have one right angle, and (2) oblique-angled triangles, all of whose angles are oblique; subdivided into (a) acute-angled tri anglos, which have all their angles acute; and (b) obtuse-angled triangles, which have one obtuse angle. The sides and angles of a triangle are called its elements; the side on which it is supposed to stand is called the base, and the vertex of the is birectangular, when it has two right angles, and tri rectangular, when it has three right angles. A tri rectangular triangle is one-eighth of the surface of the sphere, and is taken as the unit of measure for polyhedral angles. Two spherical triangles are polar, when the angles of the one are supplements of the sides of the other, taken in the same order. A spherical triangle is quadrantal, when one of its sides is equal to 90°. [SPHERICAL.] (5) Supplemental triangle : (SUPPLEMENTAL.] (6) Triangle of forces : Mech .: A term applied to that proposition which a erts that if three forces, represented in magni tude and direction by the sides of a triangle taken in order, act upon a point, they will be in equilibrium; and conversely, if three forces acting upon a point, and in equilibrium, be represented in direction by the sides of a triangle taken in order, they will also be represented in magnitude by the sides of that triangle. (7) Triangle of He elbach : Anat .: A triangular interval at the part of the abdominal wall through which the direct inguinal hernia pa es. (8) Triangle of Scarpa : Anat .: A triangular depre ion between the muscles covering the outer side of the femur and the adductor muscles on the inner side. It affords a pa age for the femoral artery.