The Method of Mechanical Theorems convenient to use a little bit of coordinate geometry. If a sphere of radius 1 is placed with its center at "x" = 1, the vertical cross sectional radius formula_2 at any "x" between 0 and 2 is given by the following formula: The mass of this cross section, for purposes of balancing on a lever, is proportional to the area: Archimedes then considered rotating the triangular region between "y" = 0 and "y" = "x" and "x" = "2" on the "x"-"y" plane around the "x"-axis, to form a cone. The cross section of this cone is a circle
Micro Four Thirds system Four Thirds and MFT measures 18 mm × 13.5 mm (22.5 mm diagonal), with an imaging area of 17.3 mm × 13.0 mm (21.6 mm diagonal), comparable to the frame size of 110 film.<ref name='Olympus-Europe 4/3'></ref> Its area, ca. 220 mm², is approximately 30% less than the quasi-APS-C sensors used in other manufacturers' DSLRs; it is around 9 times larger than the 1/2.3" sensors typically used in compact digital cameras. The Four Thirds system uses a 4:3 image aspect ratio, like compact digital cameras. In comparison, DSLRs usually adhere to the 3:2 aspect ratio of the traditional 35 mm format.