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en's morris. See Morris. -- Nine points circle (Geom.), a circle so related to any given triangle as to pass through the three points in which the perpendiculars from the angles of the triangle upon the opposite sides (or the sides produced) meet the sides. It also passes through the three middle points of the sides o…

Having oblique angles; as, an oblique-angled triangle.

Having an obtuse angle; as, an obtuse-angled triangle.

id bounded by eight faces. The regular octahedron is contained by eight equal equilateral triangles.

That point in which the three perpendiculars let fall from the angles of a triangle upon the opposite sides, or the sides produced, mutually intersect.

A triangle having three acute angles.

A figure composed of two equilateral triangles intersecting so as to form a six-pointed star, -- used in early ornamental art, and also with superstitious import by the astrologers and mystics of the Middle Ages.

n run. Equilateral pitch is where the two sloping sides with the span form an equilateral triangle. -- Pitch of a plane (Carp.), the slant of the cutting iron. -- Pitch pipe, a wind instrument used by choristers in regulating the pitch of a tune. -- Pitch point (Gearing), the point of contact of the pitch lines of t…

or contrast as possible. -- Polar projection. See under Projection. -- Polar spherical triangle (Spherics), a spherical triangle whose three angular points are poles of the sides of a given triangle. See 4th Pole, 2. -- Polar whale (Zoöl.), the right whale, or bowhead. See Whale.

.), a figure which can not be divided into any other figure more simple than itself, as a triangle, a pyramid, etc. -- Prime meridian (Astron.), the meridian from which longitude is reckoned, as the meridian of Greenwich or Washington. -- Prime minister, the responsible head of a ministry or executive government; app…

To extend; -- applied to a line, surface, or solid; as, to produce a side of a triangle.

A solid figure contained by a plane rectilineal figure as base and several triangles which have a common vertex and whose bases are sides of the base.

eom.), the theorem that the square described upon the hypothenuse of a plane right-angled triangle is equal to the sum of the squares described upon the other two sides. -- Pythagorean system (Astron.), the commonly received system of astronomy, first taught by Pythagoras, and afterward revived by Copernicus, whence i…

quadrant; also, included in the fourth part of a circle; as, quadrantal space. Quadrantal triangle, a spherical triangle having one side equal to a quadrant or arc of 90º. -- Quadrantal versor, a versor that expresses rotation through one right angle.

es, the opposite sides parallel, and four right angles; square. Figures, some round, some triangle, some quadrate. Foxe.

tuted for that quantity. -- Reciprocal figures (Geom.), two figures of the same kind (as triangles, parallelograms, prisms, etc.), so related that two sides of the one form the extremes of a proportion of which the means are the two corresponding sides of the other; in general, two figures so related that the first co…

ving surface a solid (called a solid of revolution); as, the revolution of a right-angled triangle about one of its sides generates a cone; the revolution of a semicircle about the diameter generates a sphere.

These are strong arches, meeting and crossing one another, dividing the whole space into triangles, which are then filled by vaulted construction of lighter material. Hence, an imitation of one of these in wood, plaster, or the like.

Containing a right angle or right angles; as, a right-angled triangle.

Having the sides and angles unequal; -- said of a triangle.