# plane+figure

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**Genus–differentia definition**— Part of a series on Aristotelianism …102

**Complex number**— A complex number can be visually represented as a pair of numbers forming a vector on a diagram called an Argand diagram, representing the complex plane. Re is the real axis, Im is the imaginary axis, and i is the square root of –1. A complex… …103

**PLAN**— ANE. adj. T. de Mathématiques. Il n est guère usité que dans ces locutions : Surface plane, angle plan, figure plane, Surface sur laquelle une ligne droite peut s appliquer complétement dans toutes les directions ; angle tracé sur une surface… …104

**Centroid**— of a triangle In geometry, the centroid, geometric center, or barycenter of a plane figure or two dimensional shape X is the intersection of all straight lines that divide X into two parts of equal moment about the line. Informally, it is the… …105

**Orientation (geometry)**— This article is about the orientation or attitude of an object in space. For orientation as a property in linear algebra, see Orientation (vector space). Changing orientation of a rigid body is the same as rotating the axes of a reference frame… …106

**Eigenvalue, eigenvector and eigenspace**— In mathematics, given a linear transformation, an Audio|De eigenvector.ogg|eigenvector of that linear transformation is a nonzero vector which, when that transformation is applied to it, changes in length, but not direction. For each eigenvector… …107

**symmetry**— /sim i tree/, n., pl. symmetries. 1. the correspondence in size, form, and arrangement of parts on opposite sides of a plane, line, or point; regularity of form or arrangement in terms of like, reciprocal, or corresponding parts. 2. the proper or …108

**Cavalieri's principle**— Two stacks of coins with the same volume In geometry, Cavalieri s principle, sometimes called the method of indivisibles, named after Bonaventura Cavalieri, is as follows:[1] 2 dimensional case: Suppose two regions in a plane are included between …109

**solid of revolution**— Etymology: solid (III) : a mathematical solid conceived as formed by the revolution of a plane figure about an axis in its plane * * * a three dimensional figure formed by revolving a plane area about a given axis. [1810 20] * * * solid of… …110

**Anticlinal axis**— Axis Ax is, n.; pl. {Axes}. [L. axis axis, axle. See {Axle}.] A straight line, real or imaginary, passing through a body, on which it revolves, or may be supposed to revolve; a line passing through a body or system around which the parts are… …