Cut-the-knot is a free, advertisement-funded educational website maintained by Alexander Bogomolny and devoted to popular exposition of many topics in mathematics

Mathematics

Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

. The site has won more than 20 awards from scientific and educational publications, including a Scientific American

Scientific American

Scientific American is a popular science magazine. It is notable for its long history of presenting science monthly to an educated but not necessarily scientific public, through its careful attention to the clarity of its text as well as the quality of its specially commissioned color graphics...

 Web Award in 2003, the Encyclopædia Britannica

Encyclopædia Britannica

The Encyclopædia Britannica , published by Encyclopædia Britannica, Inc., is a general knowledge English-language encyclopaedia that is available in print, as a DVD, and on the Internet. It is written and continuously updated by about 100 full-time editors and more than 4,000 expert...

's Internet Guide Award, and Science Magazine

Science (journal)

Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

's NetWatch award. Its name is a reference to the legend of Alexander the Great's solution to the Gordian knot

Gordian Knot

The Gordian Knot is a legend of Phrygian Gordium associated with Alexander the Great. It is often used as a metaphor for an intractable problem solved by a bold stroke :"Turn him to any cause of policy,...

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Cut-the-knot's manifesto states that "Judging Mathematics by its pragmatic value is like judging symphonia by the weight of its score," and describes the site as "a resource that would help learn, if not math itself, then, at least, ways to appreciate its beauty."
The site is designed for teachers, children and parents, and anyone else curious about mathematics, with an eye to educating, encouraging interest, and provoking curiosity. Many mathematical ideas are illustrated by applet

Applet

In computing, an applet is any small application that performs one specific task that runs within the scope of a larger program, often as a plug-in. An applet typically also refers to Java applets, i.e., programs written in the Java programming language that are included in a web page...

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CTK wiki (powered by PmWiki

PmWiki

PmWiki is wiki software written by Patrick R. Michaud in the PHP programming language. It is free software, licensed under the terms of the GNU General Public License.-Design focus:...

) extends the main site with additional mathematical content, especially that with more complicated formulae than available on the main site.