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COMMENTS
| A magic triangle of Yates,with nine numbers a,b,c,d,e,f,g,h,i has the form
............a
..........d...f
.........e.....g
........b..h..i..c
The corner sum C = a+b+c and magic side-sum S = a+d+e+b = b+h+i+c = a+f+g+c are related by C=3*(S - 15). Since here, 1+2+3 =< C =< 7+8+9, we have 17 =< S =< 23. Finally,an argument based on contradiction proof eliminates the values of 18 and 22 for S.
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EXAMPLE
| All the magic triangles are illustrated:
.....1............1............4............3............7
...9...6........8...9........8...1........8...7........3...6
..5.....7......6.....2......3.....9......4.....2......5.....1
.2..8..4..3...4..5..3..7...5..7..2..6...6..5..1..9...8..2..4..9
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