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The Making Method of the First Tangent Table in the World in 8th Century, China

Jochi Shigeru

The first tangent table was already reported by Dr. Christopher Cullen in 1982. It is expressed in the character, not formula, at the Dayan-li almanac. This table, however, has some error because the original wasn't correct. Through Prof. Liu Jinyi, Prof. Zhao Chengqiu and Prof. Qu Anjing's studies, the original table became distinct.

The author analyzed this table then concluded that 1 Chinese degree is 360/364 degree, not 360/365.25 degree. Chinese astronomer made the circle model, then measured the value of function of tangent. Therefore we can conclude that this table is not imported from other countries, it was made individually in China.

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