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The ellipsis (/ ə ˈ l ɪ p s ɪ s /, plural ellipses; from Ancient Greek: ἔλλειψις, élleipsis, lit. ' leave out ' [1]), rendered ..., alternatively described as suspension points [2]: 19 /dots, points [2]: 19 /periods of ellipsis, or ellipsis points, [2]: 19 or colloquially, dot-dot-dot, [3] [4] is a punctuation mark consisting of a series of three dots.
Every triangle can be inscribed in an ellipse, called its Steiner circumellipse or simply its Steiner ellipse, whose center is the triangle's centroid. Every triangle has an infinitude of inscribed ellipses. One of them is a circle, and one of them is the Steiner inellipse which is tangent to the triangle at the midpoints of the sides.
An ellipse (red) obtained as the intersection of a cone with an inclined plane. Ellipse: notations Ellipses: examples with increasing eccentricity. In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant.
An ellipse has two axes and two foci Unlike most other elementary shapes, such as the circle and square , there is no algebraic equation to determine the perimeter of an ellipse . Throughout history, a large number of equations for approximations and estimates have been made for the perimeter of an ellipse.
The gallery may also be in the form of an ellipse or ellipsoid, [4] with an accessible point at each focus. In this case, when a visitor stands at one focus and whispers, the line of sound emanating from this focus reflects directly to the focus at the other end of the gallery, where the whispers may be heard.
An ellipse can be defined as the locus of points for which the sum of the distances to two given foci is constant. A circle is the special case of an ellipse in which the two foci coincide with each other. Thus, a circle can be more simply defined as the locus of points each of which is a fixed distance from a single given focus.
An ellipse can be drawn (by computer or by hand), if besides the center at least two conjugate points on conjugate diameters are known. In this case either one determines by Rytz's construction the vertices of the ellipse and draws the ellipse with a suitable ellipse compass; or uses an parametric representation for drawing the ellipse.
Using these concepts, "two diameters are conjugate when each is the polar of the figurative point of the other." [5] Only one of the conjugate diameters of a hyperbola cuts the curve. The notion of point-pair separation distinguishes an ellipse from a hyperbola: In the ellipse every pair of conjugate diameters separates every other pair. In a ...