| The ratio of the circumference of a circle to its diameter is about 3.14, and provided that we round off the second decimal place and regard the ratio as 3.2, the circumference of a circle whose diameter is 1 shaku becomes 3.2 shaku, and in ancient China, this 3.2 shaku was equalized with 4 ata. |
円周率は約 3.14 であるが、これを 3.2 で近似すると、径 1 尺の円 (数学)の円周は 3.2 尺となり、これを 4 咫とした。 |