Circle a triangle whose base has the length of the circle's circumference and whose height equals the circle's radius, which comes to multiplied by the radius squared: Equivalently, denoting diameter by "d", that is, approximately 79% of the circumscribing square (whose side is of length "d"). The circle is the plane curve enclosing the maximum area for a given arc length. This relates the circle to a problem in the calculus of variations, namely the isoperimetric inequality. Equation of a circle<br> In an "x"–"y" Cartesian coordinate system, the circle with centre coordinates ("a", "b") and radius "r" is the set of
Straight from the Hart Straight from the Hart Straight from the Hart is a 2011 autobiography by Canadian professional wrestler Bruce Hart. The book chronicles Hart's childhood in Calgary as a member of the Albertan Hart wrestling family, his career in the wrestling industry to his later life as a trainer. It was published by ECW Press. The book is one of a long line of books by or about members of Hart's family. The book was first announced in May 2010. In March Hart was interviewed about the book on WDFN Wrestling Elite and Monday Night Mayhem. On Monday Night Mayhem Hart explained