Magic circle (mathematics)

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Yang Hui's magic concentric circles - numbers on each circle and diameter (ignoring the middle 9) sum to 138 Yang Hui magic circle.svg
Yang Hui's magic concentric circles numbers on each circle and diameter (ignoring the middle 9) sum to 138

Magic circles were invented by the Song dynasty (9601279) Chinese mathematician Yang Hui (c. 12381298). It is the arrangement of natural numbers on circles where the sum of the numbers on each circle and the sum of numbers on diameter are identical. One of his magic circles was constructed from 33 natural numbers from 1 to 33 arranged on four concentric circles, with 9 at the center.

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Yang Hui magic circles

Yang Hui's magic circle series was published in his Xugu Zhaiqi Suanfa《續古摘奇算法》 (Sequel to Excerpts of Mathematical Wonders) of 1275. His magic circle series includes: magic 5 circles in square, 6 circles in ring, magic eight circle in square magic concentric circles, magic 9 circles in square.

Yang Hui magic concentric circle

Yang Hui's magic concentric circle has the following properties

Yang Hui magic eight circles in a square

Yang Hui 8 magic circles in a square Ba Zhen Tu YangHui magic circle 1.jpg
Yang Hui 8 magic circles in a square 八阵图

64 numbers arrange in circles of eight numbers, total sum 2080, horizontal / vertical sum = 260.

From NW corner clockwise direction, the sum of 8-number circles are:

40 + 24 + 9 + 56 + 41 + 25 + 8 + 57 = 260
14 + 51 + 46 + 30 + 3 + 62 + 35 + 19 = 260
45 + 29 + 4 + 61 + 36 + 20 + 13 + 52 = 260
37 + 21 + 12 + 53 + 44 + 28 + 5 + 60 = 260
47 + 31 + 2 + 63 + 34 + 18 + 15 + 50 = 260
7 + 58 + 39 + 23 + 10 + 55 + 42 + 26 = 260
38 + 22 + 11 + 54 + 43 + 27 + 6 + 59 = 260
48 + 32 + 1 + 64 + 33 + 17 + 16 + 49 = 260

Also the sum of the eight numbers along the WE/NS axis

14 + 51 + 62 + 3 + 7 + 58 + 55 + 10 = 260
49 + 16 + 1 + 64 + 60 + 5 + 12 + 53 = 260

Furthermore, the sum of the 16 numbers along the two diagonals equals to 2 times 260:

40 + 57 + 41 + 56 + 50 + 47 + 34 + 63 + 29 + 4 + 13 + 20 + 22 + 11 + 6 + 27 = 2 × 260 = 520

Yang Hui Magic Nine circles in a square

Yang Hui 9 magic circles in a square Lian Huan Tu Yanghui magic circle 2.jpg
Yang Hui 9 magic circles in a square 连环图

72 number from 1 to 72, arranged in nine circles of eight numbers in a square; with neighbouring numbers forming four additional eight number circles: thus making a total of 13 eight number circles:

NWNNE
x1x2
WCE
x3x4
SWSSE

Extra circle x1 contains numbers from circles NW, N, C, and W; x2 contains numbers from N, NE, E, and C; x3 contains numbers from W, C, S, and SW; x4 contains numbers from C, E, SE, and S.

Ding Yidong magic circles

Ding Yidong magic circles - numbers on each circle (solid colour) sum to 200 and numbers on each diameter (dashed grey) sum to 325 Ding Yidong magic circle.svg
Ding Yidong magic circles numbers on each circle (solid colour) sum to 200 and numbers on each diameter (dashed grey) sum to 325

Ding Yidong was a mathematician contemporary with Yang Hui. In his magic circle with 6 rings, the unit numbers of the 5 outer rings, combined with the unit number of the center ring, form the following magic square:

492
357
816

Method of construction:

Let radial group 1 =1,11,21,31,41
Let radial group 2=2,12,22,32,42
Let radial group 3=3,13,23,33,43
Let radial group 4=4,14,24,34,44
Let radial group 6=6,16,26,36,46
Let radial group 7=7,17,27,37,47
Let radial group 8=8,18,28,38,48
Let radial group 9=9,19,29,39,49
Let center group =5,15,25,35,45

Arrange group 1,2,3,4,6,7,9 radially such that

number 5 on group 1 radial
number 10 on group 2 radial
number 15 on group 3 radial
...
number 45 on group 9 radial

Cheng Dawei magic circles

Cheng Dawei, a mathematician in the Ming dynasty, in his book Suanfa Tongzong listed several magic circles

Extension to higher dimensions

Andrews's sphere with numbers 1 to 62 arranged along intersections of 5 circles of latitude (dashed grey) and 6 circles of longitude (coloured solid) Andrews magic sphere.svg
Andrews's sphere with numbers 1 to 62 arranged along intersections of 5 circles of latitude (dashed grey) and 6 circles of longitude (coloured solid)

In 1917, W. S. Andrews published an arrangement of numbers 1, 2, 3, and 62 in eleven circles of twelve numbers each on a sphere representing the parallels and meridians of the Earth, such that each circle has 12 numbers totalling 378. [1]

Relationship with magic squares

Magic circle derived from magic square Magic circle derived from magic square.svg
Magic circle derived from magic square

A magic circle can be derived from one or more magic squares by putting a number at each intersection of a circle and a spoke. Additional spokes can be added by replicating the columns of the magic square.

In the example in the figure, the following 4×4 most-perfect magic square was copied into the upper part of the magic circle. Each number, with 16 added, was placed at the intersection symmetric about the centre of the circles. This results in a magic circle containing numbers 1 to 32, with each circle and diameter totalling 132. [1]

61549
310516
138112
121147

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Yang Hui, courtesy name Qianguang (謙光), was a Chinese mathematician and writer during the Song dynasty. Originally, from Qiantang, Yang worked on magic squares, magic circles and the binomial theorem, and is best known for his contribution of presenting Yang Hui's Triangle. This triangle was the same as Pascal's Triangle, discovered by Yang's predecessor Jia Xian. Yang was also a contemporary to the other famous mathematician Qin Jiushao.

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References

  1. 1 2 W. S. Andrews, MAGIC SQUARES AND CUBES, Second Edition, Revised and Enlarged, Open Court Basic Readers (1917), page 198, fig.337