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An instrument of percussion, usually made of a rod of steel, bent into the form of a triangle, open at one angle, and sounded by being struck with a small metallic rod.

Having three angles; triangular.

Having acute angles; as, an acute-angled triangle, a triangle with every one of its angles less than a right angle.

ase of a figure to the summit, or to the side parallel to the base; as, the altitude of a triangle, pyramid, parallelogram, frustum, etc.

An obtuse-angled figure, esp. and obtuse-angled triangle. [Obs.]

urface included within any given lines; superficial extent; as, the area of a square or a triangle.

he fifth proposition of the first book of Euclid, "The angles at the base of an isosceles triangle are equal to one another." [Sportive] "A schoolboy, stammering out his Asses' Bridge." F. Harrison. -- To make an ass of one's self, to do or say something very foolish or absurd.

ute the distances and positions of any points or objects connected with it by a system of triangles. Lyman.

Containing or having two right angles; as, a birectangular spherical triangle.

One line or radius falling perpendicularly on another; as, the catheti of a right-angled triangle, that is, the two sides that include the right angle. Barlow.

northern constellation near the pole. Its head, which is in the Milky Way, is marked by a triangle formed by three stars of the fourth magnitude. See Cassiopeia.

An instrument for constructing triangles in marine surveying, etc.

The center of a circle that circumscribes a triangle.

ar to ninepins, except that only three pins are used, which are set up at the angles of a triangle.

To occupy the same place in space, as two equal triangles, when placed one on the other. If the equator and the ecliptic had coincided, it would have rendered the annual revoluton of the earth useless. Cheyne.

A solid of the form described by the revolution of a right- angled triangle about one of the sides adjacent to the right angle; - - called also a right cone. More generally, any solid having a vertical point and bounded by a surface which is described by a straight line always passing through that vertical point; a sol…

-- Conjugate point (Geom.), an acnode. See Acnode, and Double point. -- Self-conjugate triangle (Conic Sections), a triangle each of whose vertices is the pole of the opposite side with reference to a conic.

rst supposed becoming now the conclusion or inference. Thus, if two sides of a sides of a triangle are equal, the angles opposite the sides are equal; and the converse is true, i.e., if these angles are equal, the two sides are equal.

(Crystalloq.) A solid related to a tetrahedron, and contained under twelve equal triangles.

uced or inferred; derivable by reasoning, as a result or consequence. All properties of a triangle depend on, and are deducible from, the complex idea of three lines including a space. Locke.