# conic sections

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## conic sections

(kon -ik) (conics) A family of curves that are the locus of a point that moves so that its distance from a fixed point (the focus) is a constant fraction of its distance from a fixed line (the directrix). The fraction, e , is the eccentricity of the conic. The value of the eccentricity determines the form of the conic. If e is less than 1 the conic is an ellipse. A circle is a special case of this with e = 0. If e = 1 the conic is a parabola and if e exceeds 1 the conic is a hyperbola.

These curves are known as conic sections because they can be obtained by taking sections of a right circular cone at different angles: a horizontal section gives a circle, an inclined one an ellipse, one parallel to the slope of the cone is a parabola, and one with an even greater inclination is a hyperbola (see illustration). Conics are important in astronomy since they represent the paths of bodies that move in a gravitational field. See also orbit.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## Conic sections

Circle, ellipse, parabola, and hyperbola; all produced by cutting a plane through a cone at different angles. Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
So, observing once more that consecutive conic sections share a common point, the third shaping equation is obtained from (5) at [[theta].sub.F] = [[theta].sub.Fn-1]:
Although we can calculate the next term [[phi].sub.m+2] directly, the conic sections allow us to easily "track" the movements of the points from [mathematical expression not reproducible].
The second part of Problem 1 considers studying Conic sections.
It should be noted that the algebraic expression that refers to all possible parabolas is derived from the general, second-degree equation of the conic sections, a[x.sup.2] + 2hxy + [by.sup.2] + 2gx + 2fy + c = 0.
On page 81 (Hypatia's work) students learn that conic sections yield four kinds of curves, but only three are presented (the circle, ellipse, and parabola).
At twelve years of age Pascal discovered Euclid's axioms unaided; at sixteen he wrote a treatise on conic sections, and at eighteen he invented a calculating machine.
Khayyam states that the solution of this cubic needs the use of conic sections and that it cannot be solved by ruler and compass methods, a result which would not be proved for another 750 years.
Moreira, "Main-reflector shaping of omnidirectional dual reflectors using local conic sections," IEEE Transactions on Antennas and Propagation, vol.
The authors provide a precalculus review before covering limits, differentiations, the applications of the derivative, the integral, applications of the integral, techniques of integration, advanced applications of the integral and Taylor polynomials, differential equations, infinite series, parametric equations, polar coordinates, and conic sections over the bookAEs eleven chapters.
After reviewing prerequisites, the chapters consider such topics as equations and graphs, exponential and logarithmic functions, matrices and determinants, conic sections, and probability and statistics.
7 Conic sections cannot be plotted directly with many dynamic geometry software packages, and a conic section only appears as the locus of some point.
Eight pages of "quickies" are followed by 26 pages of more complex problems in the areas of combinatorics and number theory, functions and polynomials, expression and identities, numerical approximation, algebraic inequalities, trigonometric inequalities, geometric inequalities, the triangle, Cevian lines, central symmetry, conic sections, solid geometry, higher dimensions, vectors and matrices, and calculus.

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