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
Circle line party Circle line party A Circle line party is a type of subway party occasionally held on the Circle line of the London Underground. Although the time and place of these parties is planned, the event itself occurs spontaneously, as each participant decides for themselves what sort of revelry, costume, decorations, snacks, libations and guests to bring to the party. The participants decorate the carriages festively, and play music, either live or on portable sound systems, disguised to appear as normal luggage. Other activities include setting up pole-dancing poles on the trains. Free drinks, snacks and sweets are provided, often being