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
Outer Circle railway line Belgrave and Lilydale lines) with Oakleigh station to the south, via Riversdale on what is now the Alamein line. The final section was north from Riversdale through to Fairfield station (then called Fairfield Park station). There was also a branch line from the closed Waverley Road station (near the modern East Malvern station) to Darling and Burnley. This was the first section of what is now the Glen Waverley line and was opened a few weeks before the Outer Circle. When opened the line was in length, and had 11 stations, all provided with twin platforms and crossing loops. Provision