![arithmetic – Can you assemble a nonagon with 47 rods? arithmetic – Can you assemble a nonagon with 47 rods?](https://thefuntrove.com/wp-content/uploads/https://cdn.sstatic.net/Sites/puzzling/Img/apple-touch-icon@2.png?v=a7ebbe6c6b60)
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Stiv’s Diabolical Instruments now presents a bundle of precisely 47 equal-length rods that may be joined by hinges at their ends – and solely the ends – to kind planar linkages (i.e. all hinge axes are parallel to the airplane containing the rods and rod thickness is uncared for).
With 35 of those rods you may make a inflexible linkage containing the vertices of a daily heptagon:
Now you wish to do the identical for a daily nonagon. But the most effective identified bracing of a daily nonagon makes use of 51 rods, greater than you could have from one bundle:
Nevertheless it’s doable to kind a inflexible linkage containing the vertices of a daily nonagon utilizing solely 47 rods by imagining that you’ve 7 extra rods, making a totally symmetric ($D_{18}$ symmetry, similar as that of the nonagon) inflexible linkage with these 54 rods and eradicating 7 redundant rods. What does the 47-rod linkage appear to be?
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