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
The Doll that Came Straight from Fairyland a cannon and a magical balloon, but only replies that his godmother should give him what she thinks best. In response, Fairy Zigzag instead asks Princess Pansy what she would like. Princess Pansy asks for a fine clay doll. The Fairy Zigzag creates a magical doll straight from fairyland and then leaves the party. The Prince is left without a gift from his fairy godmother. Princess Pansy names the doll Lady Emmelina and in the days following the party becomes bewitched by the doll. Prince Perfection gets jealous of Lady Emmelina when his sister no longer plays with him. Missing