Person: Yang, Xiahou
Xiahou Yang was a Chinese mathematician who wrote the text Xiahou Yang suanjing (Xiahou Yang's Mathematical Manual).
Mathematical Profile (Excerpt):
 Nothing is known of Xiahou Yang except as the supposed author of the Xiahou Yang suanjing (Xiahou Yang's Mathematical Manual).
 What we have done is to use the best available evidence for the dates when the Xiahou Yang suanjing was written and deduce approximate dates for Xiahou Yang from that.
 We have comments by Zhang Qiujian which criticise the accuracy of one of the solutions given in the Xiahou Yang suanjing (Xiahou Yang's Mathematical Manual).
 Xiahou Yang notes that to multiply a number by 10, 100, 1000, or 10000 all that needs to be done is that the rods on the counting board are moved forwards by 1, 2, 3, or 4 decimal places.
 What is significant here is that Xiahou Yang seems to understand not only positive powers of 10 but also decimal fractions as negative powers of 10.
 Although Xiahou Yang has no symbol for 0 in an empty place, there is good evidence from his description of moving numbers to the right and left that he at least has a virtual zero in mind despite the lack of a symbol.
 In particular some of the problems dealing with areas in the Xiahou Yang suanjing (Xiahou Yang's Mathematical Manual) use incorrect formulae.
Born about 400, China. Died about 470, China.
View full biography at MacTutor
Tags relevant for this person:
Ancient Chinese, Chinese, Origin China
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 @JJO'Connor
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References
Adapted from other CC BYSA 4.0 Sources:
 Oâ€™Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive