Square root

In mathematics, a square root of a number a is a number y such that y² = a, in other words, a number y whose square (the result of multiplying the number by itself, or y × y) is a. For example, 4 and −4 are square roots of 16 because 4² = (−4)² = 16.

Every non-negative real number a has a unique non-negative square root, called the principal square root, which is denoted by √a, where √ is called the radical sign or radix. For example, the principal square root of 9 is 3, denoted √9 = 3, because 3² = 3 × 3 = 9 and 3 is non-negative. The term whose root is being considered is known as the radicand. The radicand is the number or expression underneath the radical sign, in this example 9.

Every positive number a has two square roots: √a, which is positive, and −√a, which is negative. Together, these two roots are denoted ± √a (see ± shorthand). Although the principal square root of a positive number is only one of its two square roots, the designation "the square root" is often used to refer to the principal square root. For positive a, the principal square root can also be written in exponent notation, as a^1/2.

Square Roots

Square Roots (previously called the Folk & Roots Festival) is a two- to three-day music festival that has been held each summer in the Lincoln Square neighborhood in Chicago since 1998. Organized by the Old Town School of Folk Music and the Lincoln Square Chamber of Commerce, the festival features world music and dance performances from a variety of genres with particular emphasis on folk and world music.

History

The Folk & Roots Festival began in 1998 and was coordinated solely by the Old Town School of Folk Music. Each year the event was held at Welles Park in Lincoln Square. The festival showcased a variety of performances from different musical traditions. For instance, in 2001, the festival hosted, among others, the Super Rail Band from Mali, Nigerian afrobeat musician Femi Kuti, and the Texan country band The Flatlanders. It also featured well-known folk performers as well, such as Patti Smith and Richard Thompson. The lineup of performances at Folk & Roots festivals have been described as "eclectic." In addition to performances, The Folk & Roots Festival also held dance workshops and events for children.

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.