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Conic Spiral (Posted on 2009-08-06) Difficulty: 3 of 5
A string is wound around a cone with base radius 1 cm and slant height 10 cm. The string is wrapped in a helical manner, as if a strand of lights decorating a Christmas tree, except that it is pulled taut around the cone so as to have no local "wiggles", thus making what is known mathematically as a geodesic curve on the surface of the cone.

What is the maximum length of such a spiral around the cone before it starts to intersect itself?

  Submitted by Jer    
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Solution: (Hide)
10/cos(18) or about 10.5146 cm.

In general the maximum length is the slant height divided by the cosine of half the vertex angle formed by the net of the cone.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re: computer solutionHarry2009-08-06 21:07:15
Solutioncomputer solutionCharlie2009-08-06 17:38:33
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