Sangaku Journal of Mathematics Published by the Association for the Development of Education, Sofia, Bulgaria About this Journal   |   Editorial Board  |   Instructions for Authors   |   Review Process   |   Links 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 9 (2025) Hiroshi Okumura, The arbelos in Wasan geometry, Nishimura's problem, pp. 1-4. Hiroshi Okumura, The arbelos in Wasan geometry, Shinohara's problem, pp. 5-8. Volume 8 (2024) J. Marshall Unger, Notes on the six-segment theorem, pp. 1-8. Kousik Sett, An Additional Property of Problem 3 and a Solution to Problem 4 of Problems 2023-1, pp. 9-14. Kousik Sett, Two Beautiful Sangaku Theorems, pp. 15-20. J. Marshall Unger, A Summary of Sanpo tai kajo no daishu by Aida Yasuaki, pp. 21-32. Volume 7 (2023) Hiroshi Okumura, A rare sangaku problem involving three congruent circles, pp. 1-8. Hiroshi Okumura, Problems 2023-1, pp. 9-12. Paris Pamfilos, Note on a sangaku like construction of X(55), pp. 13-15. Vishwesh Ravi Shrimali, Solution for Problems 2 and 3 of Problems 2023-1, pp. 16-19. Kousik Sett, Solution for Problems 2 and 3 of Problems 2023-1 by Vishwesh Ravi Shrimali (ERRATA), p. 20. Ercole Suppa and Marian Cucoanes, Solution of Problems 2023-1-6, pp. 21-28. Hiroshi Okumura and Kousik Sett, The arbelos in Wasan geometry: the Aida arbelos and Problem 2023-1-5, pp. 29-31. Hiroshi Okumura, A configuration arising from Problem 2023-1-1, pp. 32-34. Kai-Uwe Ekrutt and Floor van Lamoen, Further notes on Tamura’s problem in the general arbelos, pp. 35-41. Paris Pamfilos, On a sangaku like configuration involving a triangle and three congruent circles, pp. 42-53. Ercole Suppa and Stanley Rabinowitz, A triad of circles associated with a triangle, pp. 54-70. Stanley Rabinowitz and Ercole Suppa, Properties of Ajima circles, pp. 71-145. Hiroshi Okumura and Dao Thanh Oai, Twin circles of a generalized arbelos with division by zero 1/0=0, pp. 146-150. Kousik Sett, Relationships between radii in a six-circle configuration, pp. 151-161. Volume 6 (2022) Hiroshi Okumura, A note on a generalization of a five circle problem, pp. 1-2. Hiroshi Okumura, A note on a generalization of a five circle problem: Part 2, pp. 3-5. Hiroshi Okumura, A note on a generalization of a five circle problem: Part 3, pp. 6-8. Li Ting Hon Stanford, A configuration involving a square and two equilateral triangles, pp. 9-12. Hiroshi Okumura, Some generalizations of five circle problems, pp. 13-18. Hiroshi Okumura, A note on circles touching two circles in a Pappus chain, pp. 19-22. Hiroshi Okumura, A note on circles touching two circles in a Pappus chain: Part 2, pp. 23-25. Kousik Sett, A note on a chain of contact circles inside a circular segment, pp. 26-30. Kousik Sett, An alternative proof of the Japanese theorem, pp. 31-33. Li Ting Hon Stanford, A simple method to explore the relationships between six areas, pp. 34-36. Hiroshi Okumura, A note on circles touching two circles in a Pappus chain: Part 3, pp. 37-40. J. Marshall Unger, A response to an open question of Rabinowitz, pp. 41-44. Volume 5 (2021) Hiroshi Okumura, The arbelos in Wasan geometry, the inscribed semicircle in the arbelos, pp. 1-8. Li Ting Hon Stanford, Ellipses inscribed in trapezoids and solutions to 2020-1 Problems 1 and 2, pp. 9-13. Hiroshi Okumura, The arbelos in Wasan geometry: Totsuka's problem (Problem 2017-3-6), pp. 14-18. Kousik Sett, A constant associated with Ikeda's theorem, pp. 19-23. Hiroshi Okumura, The arbelos in Wasan geometry: Saitoh's problem, pp. 24-31. Hiroshi Okumura, The arbelos in Wasan geometry: Atsumi's problem with division by zero calculus, pp. 32-38. Hiroshi Okumura, The arbelos in Wasan geometry: a problem in Sangaku Shōsen, pp. 39-42. J. Marshall Unger, How Wasanka did integration: The case of the Japanese wedge, pp. 43-55. 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 Li Ting Hon Stanford, A note on a sangaku problem involving the Steiner ellipse, pp. 84-85. Emmanuel Antonio Jose Garcia, Three Archimedean circles arising from equilateral triangles, pp. 86-87. Volume 3 (2019) Le Viet An and Emmanuel Antonio Jose Garcia, 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) pp. 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.