Radian

The radian is the standard unit of angular measure, used in many areas of mathematics. An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle; one radian is just under 57.3 degrees (when the arc length is equal to the radius). The unit was formerly an SI supplementary unit, but this category was abolished in 1995 and the radian is now considered an SI derived unit.

Separately, the SI unit of solid angle measurement is the steradian.

The radian is represented by the symbol rad (Unicode-encoded as U+33AD ㎭ ). An alternative symbol is ^c, the superscript letter c, for "circular measure", or the letter r, but both of those symbols are infrequently used as it can be easily mistaken for a degree symbol (°) or a radius (r). So for example, a value of 1.2 radians could be written as 1.2 rad, 1.2 r, 1.2^rad, or 1.2^c.

Definition

Radian describes the plane angle subtended by a circular arc as the length of the arc divided by the radius of the arc. One radian is the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle. More generally, the magnitude in radians of such a subtended angle is equal to the ratio of the arc length to the radius of the circle; that is, θ = s /r, where θ is the subtended angle in radians, s is arc length, and r is radius. Conversely, the length of the enclosed arc is equal to the radius multiplied by the magnitude of the angle in radians; that is, s = rθ.

Thrill Jockey

Thrill Jockey Records is an American independent record label established in 1992 in New York City by former Atlantic Records A&R representative Bettina Richards.

History

Richards started the label with $35,000 of family and personal capital, while working at a Hoboken, New Jersey, record store, and ran it from her apartment in Manhattan.

In 1995, she moved the label to Chicago, Illinois, where "rent and taxes are considerably cheaper."

Thrill Jockey offers full-length streaming of every song on every release in its catalog. "I believe if people can listen to the albums, they tend to buy them," Richards said in a 2006 interview with Chicago Reader.

Artists who have recorded on the label include Double Dagger, Future Islands, Tortoise, The Sea and Cake, High Places, Trans Am, Mouse on Mars, ADULT., Nobukazu Takemura, Bobby Conn, Tom Verlaine, Freakwater, The Zincs, The National Trust, Eleventh Dream Day, Califone, Chicago Underground Duo, Howe Gelb/Giant Sand, Oval, Town & Country, Archer Prewitt, Sam Prekop, The Lonesome Organist, OOIOO, Pit er Pat, The Fiery Furnaces, Angela Desveaux, Liturgy, Boredoms, Pontiak, and Golden Void amongst others. Artists on the label have often collaborated with other artists on the label to form spin-off groups.

Khan Academy

Khan Academy is a non-profit educational organization created in 2006 by educator Salman Khan with the aim of providing a free, world-class education for anyone, anywhere. The organization produces short lectures in the form of YouTube videos. In addition to micro lectures, the organization's website features practice exercises and tools for educators. All resources are available for free to anyone around the world. The main language of the website is English, but the content is also available in other languages.

History

The founder of the organization, Salman Khan, was born in New Orleans, Louisiana, United States to immigrant parents from Bangladesh and India. After earning three degrees from the Massachusetts Institute of Technology (a BS in mathematics, a BS in electrical engineering and computer science, and an MEng in electrical engineering and computer science), he pursued an MBA from Harvard Business School.

In late 2004, Khan began tutoring his cousin Nadia who needed help with math using Yahoo!'s Doodle notepad.When other relatives and friends sought similar help, he decided that it would be more practical to distribute the tutorials on YouTube. The videos' popularity and the testimonials of appreciative students prompted Khan to quit his job in finance as a hedge fund analyst at Connective Capital Management in 2009, and focus on the tutorials (then released under the moniker "Khan Academy") full-time.

180°

180° may refer to:

See also

Circle

A circle is a simple shape in Euclidean geometry. It is the set of all points in a plane that are at a given distance from a given point, the centre; equivalently it is the curve traced out by a point that moves so that its distance from a given point is constant. The distance between any of the points and the centre is called the radius.

A circle is a simple closed curve which divides the plane into two regions: an interior and an exterior. In everyday use, the term "circle" may be used interchangeably to refer to either the boundary of the figure, or to the whole figure including its interior; in strict technical usage, the circle is only the boundary and the whole figure is called a disk.

A circle may also be defined as a special ellipse in which the two foci are coincident and the eccentricity is 0, or the two-dimensional shape enclosing the most area per unit perimeter squared, using calculus of variations.

Terminology