Sangaku Journal of Mathematics
Published by the Association for the Development of Education, Sofia, Bulgaria
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ISSN 2534-9562

Editors-in Chief:
Hiroshi Okumura, Professor, Ph.D.
Takahanadai Maebashi Gunma, Japan
e-mail: hokmr@yandex.com
Sava Grozdev, Professor, DSc,
Association for the Development of Education, Sofia, Bulgaria
e-mail: sava.grozdev@gmail.com


Volume 4 (2020)

Hiroshi Okumura, A four circle problem and division by zero, pp.1-8.
Stanley Rabinowitz, Relationships between circles inscribed in triangles and related curvilinear triangles, pp.9-27.
Hiroshi Okumura and Ercole Suppa, A remark on an Archimedean square of a triangle associated with an arbelos, pp.28-30.
Hiroshi Okumura, Ootoba's Archimedean circles of the collinear arbelos, pp.31-35.
Problems 2020-1, pp.36-40.
Géry Huvent, Solution to Problem 2019-4, pp.41-44.
Hiroshi Okumura, A generalization of Problem 2019-4 and division by zero, pp.45-52.
Géry Huvent, Solution to Problem 2020-1 Problem 9, pp.53-60.
Hiroshi Okumura, Non-Archimedean congruent circles in Tenzan Tebikigusa Furoku, pp.61-68.
Abdilkadir Altintas, Problem 2020-2, p.69.
Kousik Sett, Solution to Problem 2020-2, pp.70-72.
Hiroshi Okumura, Solution to Problem 2017-1-6 with division by zero, pp.73-76.
Stanley Rabinowitz, Relationships between six areas, pp.77-83.
Supplementary Material. sixAreas.nb


Volume 3 (2019)

Le Viet An and Emmanuel Antonio Jose Garcıa, A pair of Archimedean incircles, pp.1-2.
Paul Yiu and Xiao-Dong Zhang, Diagram 29 in the appendix of Yojutsu Shindai, pp.3-11.
Hiroshi Okumura, A note on the arbelos in Wasan geometry, a problem in Sampo Tenzan Tebikigusa Furoku, pp.12-14.
Hiroshi Okumura, A note on the arbelos in Wasan geometry, Satoh’s problem, pp.15-16.
Problems 2019-1, pp.17-18.
Hiroshi Okumura, A note on the arbelos in Wasan geometry, Matsuda’s problem, pp.19-23.
Hiroshi Okumura, Problems 2019-2, pp.24-25.
Problems 2019-3, pp.26-28.
Kyouichi Gowa and Chieko Miyota, A sangaku problem involving four circles in a rectangle, pp.29-31.
Waldemar Pompe, On a sangaku problem involving the incircles in a square tiling: Solutions to Problems 2019-2, pp.32-35.
Tsutomu Matsuura, Hiroshi Okumura, and Saburou Saitoh, Division by zero calculus and Pompe's theorem, pp.36-40.
Hiroshi Okumura, Arbeloi determined by a chord and solutions to Problems 2017-3-8 and 2019-3-4, pp.41-50.
Stanley Rabinowitz, Relationships between six incircles, pp.51-66.
Supplementary Material. Sixincircles.zip
Hiroshi Okumura, A characterization of the golden arbelos involving an Archimedean circle, pp.67-71.
Problems 2019-4, pp.72-72.
Stanley Rabinowitz, Relationships between six excircles, pp.73-90.
Supplementary Material. Sixexcircles.zip
Hiroshi Okumura, The arbelos in Wasan geometry: Ootoba's problem and Archimedean circles, pp.91-97.
Stanley Rabinowitz, Relationships between six circumcircles, pp.98-105.
Stanley Rabinowitz, More relationships between six circles, pp.106-118.
Hiroshi Okumura, Remarks on Archimedean circles of Nagata and Ootoba, pp.119-122.
Hiroshi Okumura, Remarks on a problem involving four circles in a parallelogram, pp.123-125.


Volume 2 (2018)

Giovanni Lucca, A note on a Pappus sangaku problem and a Family of Integer Sequences, pp.1-2.
Hiroshi Okumura, A note on a problem involving a square in a curvilinear triangle, pp.3-5.
Problems 2018-1, p.6.
Abdilkadir Altintas, Problems 2018-2, p.7.
Hiroshi Okumura, A note on an isosceles triangle containing a square and three congruent circles, pp.8-10.
Abdilkadir Altintas and Hiroshi Okumura, A note on Pappus chain and a collinear theorem, pp. 11-12.
Viera Čerňanová, Solution to 2018-1 Problem 2, pp.13-14.
Viera Čerňanová, Solution to 2018-1 Problem 1, pp.15-16.
Hiroshi Okumura, Solution to 2017-3 Problem 5, pp.17-21.
Jana Fialová, Solution to 2018-2 Problem 1, pp.22-23.
Hiroshi Okumura, Solution to the problem proposed in "Solution to 2017-3 Problem 5", pp.24-26.
Hiroshi Okumura, Solution to 2017-1 Problem 4 with division by zero, pp.27-30.
Giovanni Lucca, Integer sequences and circle chains inside a tangential quadrilateral, pp.31-40.
Problems 2018-3, pp.41-42.
Hiroshi Kinoshita, An unsolved problem in the Yamaguchi's travell diary, pp.43-53.
The paper is reprinted from "Shotoh Sugaku", Volume 70 (2012) pp. 32-36 with permission from the publisher along with a supplementary Appendix.
Hiroshi Okumura, Solution to Problem 2018-3-2, pp.54-56.
Hiroshi Okumura and Saburou Saitoh, Wasan Geometry and Division by Zero Calculus, pp.57-73.
Li Ting Hon Stanford, Solution to 2017-3 Problem 3, pp.74-75.
Jana Fialová, Inscribed rectangles in a kite and a solution to 2017-1 Problem 5, pp.76-82.


Volume 1 (2017)

Hiroshi Okumura, Japanese mathematics, pp.1-6.
The paper is reprinted from "Symmetry: Culture and Science",Volume 12 (1-2) 79-86 (2001) with permission from the publisher.
Problems 2017-1, pp.7-10.
Problems 2017-2, pp.11-12.
Francisco Javier García Capitán, Solution to 2017-1 Problem 1, pp.13-15.
Yasuo Kanai and Hiroshi Okumura, A three tangent congruent circle problem, pp.16-20.
Supplementary material: animation.gif
Problems 2017-3, pp.21-23.
Hiroshi Okumura, Configurations of congruent circles on a line, pp.24-34.
Hiroshi Okumura, Theorems on two congruent circles on a line, pp.35-38.
Hiroshi Okumura, A note on the problems involving congruent circles in Tenzan Kaitei, pp.39-41.
Hiroshi Okumura, Haga's theorems in paper folding and related theorems in Wasan geometry Part 1, pp.42-56.