Ellipse

The curve drawing algorithms of Xiaolin Wu (SIGGRAPH 91) are an example.
. A more challenging task is to perform these drawing operations with antialiasing, to create a smooth-looking curve. The "Master Cutler" was the name of a train that ran between London Marylebone and Sheffield (the centre of the cutlery manufacture in the UK) during the 1950s and late 1960s. 1984). The Worshipful Company of Cutlers was one of the London livery companies, reflecting the importance of this trade in the Middle Ages. An efficient generalization to draw ellipses was invented in 1984 by Jerry Van Aken (IEEE CG&A, Sept. Cutlery gets its name from the term for a person skilled in making knives, a cutler.

Jack Bresenham at IBM is most famous for the invention of 2D drawing primitives, including line and circle drawing, using only fast integer operations such as addition and branch on carry bit. Two forms of utensil combining the functionality of various pairs of cutlery are the spork (spoon / fork) and knork (knife / fork). Often such libraries are limited and can only draw an ellipse with either the major axis or the minor axis horizontal. Plastic cutlery is made for disposable use, and is frequently used in fast food or take-away outlets and provided with airline meals. Drawing an ellipse is a common graphics primitive in standard display libraries, such as the QuickDraw and GDI interfaces on the Macintosh and Windows systems. From the nineteenth century, Electroplated Nickel Silver (EPNS) was used as a cheaper substitute; nowadays, most cutlery, including quality designs, is made from stainless steel. Einstein's contributions to modern physics may not have been discovered if it were not for ellipses. name), though steel was always used for more utilitarian knives, and pewter was used for some cheaper items, especially spoons.

Albert Einstein also used the ellipse to prove his theory of relativity by using an elliptical shaped mass. Traditionally, good quality cutlery was made from silver (hence the U.S. The general solution for a harmonic oscillator in two or more dimensions is also an ellipse, but this time with the origin of the force located at the center of the ellipse. The major items of cutlery in the western world are the knife, fork and spoon. Interestingly, the orbit of either body in the reference frame of the other is also an ellipse, with the other body at one focus. Since silverware suggests the presence of silver, the term tableware has come into use. More generally, in the gravitational two-body problem, if the two bodies are bound to each other (i.e., the total energy is negative), their orbits are similar ellipses with the common barycenter being one of the foci of each ellipse. This is probably the original meaning of the word.

Later, Isaac Newton explained this as a corollary of his law of universal gravitation. It is more usually known as silverware or flatware in the United States, where cutlery can have the more specific meaning of knives and other cutting instruments. In the 17th century, Johannes Kepler explained that the orbits along which the planets travel around the Sun are ellipses, which is Kepler's first law. Cutlery refers to any hand utensil used in preparing, serving, and especially eating food. Indian astronomer Aryabhata discovered that the orbits of the planets around the sun are ellipses in 499, which he described in his book, the Aryabhatiya [1]. Since no other curve has such a property, it can be used as an alternative definition of an ellipse.

Then all rays are reflected to a single point — the second focus. Assume an elliptic mirror with a light source at one of the foci. If the projection is a closed curve on the plane, then the curve is an ellipse or a degenerate ellipse. Similarly, any oblique projection onto a plane results in a conic section.

The stretched ellipse will have different properties (perhaps changed eccentricity and semi-major axis length, for instance), but it will still be an ellipse (or a degenerate ellipse: a circle or a line). An ellipse may be uniformly stretched along any axis, in or out of the plane of the ellipse, and it will still be an ellipse. The inverse function, the angle subtended as a function of the arc length, is given by the elliptic functions. More generally, the arc length of a portion of the circumference, as a function of the angle subtended, is given by an incomplete elliptic integral.

which can also be written as:. A good approximation is Ramanujan's:. The exact infinite series is:. The circumference of an ellipse is 4aE(e), where the function E is the complete elliptic integral of the second kind.

The area enclosed by an ellipse is , where π is Archimedes' constant. An ellipse can also be thought of as a projection of a circle: a circle on a plane at angle φ to the horizontal projected vertically onto a horizontal plane gives an ellipse of eccentricity sin φ, provided φ is not 90°. In polar coordinates, an ellipse with one focus at the origin and the other on the negative x-axis is given by the equation. It is related to and (the ellipse's semi-axes) by the formula or, if using the eccentricity, .

The semi-latus rectum of an ellipse, usually denoted (lowercase L), is the distance from a focus of the ellipse to the ellipse itself, measured along a line perpendicular to the major axis. The distance between the foci is 2ae. The ellipse shown in the image below has an eccentricity of approximately 0.8733. The greater the eccentricity is, the larger the ratio of a to b is, and therefore the more elongated the ellipse is.

The eccentricity is a positive number less than 1, or 0 in the case of a circle. or where c (the linear eccentricity of the ellipse) equals the distance from the center to either focus. The eccentricity is related to a and b by the statement. The shape of an ellipse is usually expressed by a number called the eccentricity of the ellipse, conventionally denoted e (not to be confused with the mathematical constant e).

has normal (cosφ,sinφ). A Gauss-mapped form:. where (h,k) is the center. If an ellipse is not centered at the origin of an x-y coordinate system, but again has its major axis along the x-axis, it may be specified by the equation.

which use the trigonometric functions sine and cosine. The same ellipse is also represented by the parametric equations:. The following diagram shows an ellipse demonstrating the Pythagoras equation a² = b² + c² as a special case of the non-parametric equation above (x=0, y=b). The derivation of this formula is quite instructive and not overly difficult.

An ellipse centered at the origin of an x-y coordinate system with its major axis along the x-axis is defined by the equation. The constant a equals the length of the semimajor axis; the constant b equals the length of the semiminor axis. The size of an ellipse is determined by two constants, conventionally denoted a and b. .

. Then the axes of the ellipse will lie along the eigenvectors of A, and the squares of the lengths of the axes are the inverses of the eigenvalues. An ellipse centred at the origin can be viewed as the image of the unit circle under a linear map associated with a symmetric matrix A = PDP^T, D being a diagonal matrix with the eigenvalues of A, both of which are real positive, along the main diagonal, and P being a real unitary matrix having as columns the eigenvectors of A. If the two foci coincide, then the ellipse is a circle; in other words, a circle is a special case of an ellipse, one where the eccentricity is zero.

Likewise, the semiminor axis is one half the minor axis. A semimajor axis is one half the major axis: the line segment from the center, through a focus, and to the edge of the ellipse. The line which passes through the center (halfway between the foci), at right angles to the major axis, is called the minor axis. The major axis is along the longest segment that passes through the ellipse.

The line segment which passes through the foci and terminates on the ellipse is called the major axis. If the pencil is moved around so that the string stays taut, the sum of the distances from the pencil to the pins will remain constant, satisfying the definition of an ellipse. The string will form a triangle. The pencil is placed on the paper inside the string, so the string is taut.

The pins are placed at the foci and the pins and pencil are enclosed inside the string. An ellipse can be drawn with two pins, a loop of string, and a pencil. such that B² < 4AC, where all of the coefficients are real, and where more than one solution, defining a pair of points (x, y) on the ellipse, exists. Algebraically, an ellipse is a curve in the Cartesian plane defined by an equation of the form.

For a short elementary proof of this, see Dandelin spheres. An ellipse is a type of conic section: if a conical surface is cut with a plane which does not intersect the cone's base, the intersection of the cone and plane is an ellipse. The two fixed points are called foci (plural of focus). In mathematics, an ellipse (from the Greek for absence) is a plane algebraic curve where the sum of the distances from any point on the curve to two fixed points is constant.

Elliptical redirects here, for the exercise machine, see Elliptical trainer..