Area of a circle "ds" over the whole circle formula_33 is just the arc length, which is its circumference, so this shows that the area "A" enclosed by the circle is equal to formula_34 times the circumference of the circle. Note that the area of a semicircle of radius r can be computed by the integral formula_35. By trigonometric substitution, we substitute formula_36, hence formula_37 The last step follows since the trigonometric identity formula_42 implies that formula_43 and formula_44 have equal integrals over the interval formula_45, using integration by substitution. But on the other hand, since formula_46, the sum of the two integrals is
The Doll that Came Straight from Fairyland straight on, and when he meets other people he must ask what they are thinking. In his quest, he travels across the sea, through a gorse bush and over an iceberg to a castle. Along the way he collects thoughts. These thoughts consist of the Prince's wishes for his gift: a steamboat, a cannon and a magical balloon. The gifts that the Prince had wished for earlier help him reach the castle where Lady Emmelina is waiting. Once he finds her, the Prince quickly returns home. When Princess Pansy sees her brother she hugs him while Lady Emmelina falls to