# Introduction

We wonder if you would happen to know the word, "*Wasan.*" The mathematics that developed in Japan before the Edo period, independently from the Western mathematics, is called Wasan. Western mathematics has been taught in school education since the Meiji era, causing Wasan, the indigenous mathematics of Japan, to fade from the limelight. However, Wasan was an excellent academic discipline and in no way inferior to its Western counterpart.

Wasan addressed various mathematical problems from introductory problems such as *nezumizan* (geometric progression) and *tsurukamezan* (a method of calculation based on determining the number of cranes and tortoises from the total number of their legs) to advanced problems relating to algebra and geometry, including simultaneous equations, Pi (the ratio of the circumference of a circle to its diameter), and trigonometric functions. As it also dealt with many practical problems, it was regarded as knowledge directly useful for the lives of people in agriculture or forestry, fishery, commerce, etc., and came to spread not only to the samurai class but also to the common people. It would not be an exaggeration to say that Wasan played a really significant role in contributing to the development of Japanese society in the Edo period.

The Edo period, when Wasan was at its peak, saw the publication of many books related to the subject. Our National Diet Library houses many of such Wasan books. In these books, the same mathematical concepts that are also approached by Western mathematics are expressed with terms and symbols totally different from those of Western mathematics, and the problems are likewise solved from different angles. A quick glance at the differences in notation between Wasan and Western mathematics is highly intriguing, and the beautifully drawn geometrical figures surely captivate the eyes of the viewers.

This electronic exhibition consists of the following two parts: Part 1 provides simple and straightforward explanations on the history of Wasan, a genealogy of Wasan scholars represented by Seki Takakazu, etc., as well as the posts "Column" to deepen your understanding of mathematics in conjunction with such explanations. In Part 2, the "Wasan Reference Library" posts the full-text images of major reference materials related to Wasan housed by our Library in conjunction with their bibliographical introduction.

Please, enjoy the fascinating world of Wasan, savoring its delightful difference from Western mathematics.

*The texts in this electronic exhibition were written by Mr. Sato Ken'ichi (Associate Professor, University of Electro-Communications) and Orita Hiroharu (Library Counsellor of the National Diet Library) (as of when they were written).

The following table shows the respective sections each author was responsible for:

Part 1: | Chapters 1 to 6 | Sato Ken'ichi |
---|---|---|

Part 1: | Column | Orita Hiroharu |

Part 2: | Wasan Materials housed in Japan | Orita Hiroharu |

Part 2: | Wasan Materials housed by the National Diet Library | Orita Hiroharu |

Part 2: | Wasan Library | Sato Ken'ichi |