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FindRoot anomaly (example from Mathematica Tutorial)

• To: mathgroup at smc.vnet.net
• Subject: [mg72118] FindRoot anomaly (example from Mathematica Tutorial)
• From: howardfink at gmail.com
• Date: Wed, 13 Dec 2006 06:38:51 -0500 (EST)

FindRoot[3Cos[x] == Log[x], {x, 1}] is on page 12 of the tutorial that
starts up in Mathematica 5.
I was interested in how the seed affects the answer, so I made a table

sol = Table[FindRoot[3Cos[x] == Log[x], {x, b}], {b, 100}];

and then plotted the solutions

ListPlot[x /. sol]

I got a nice table, but the seed of 22 returns  {x -> -207.932 +
1.39227 i]}

so the plot returns the error:
Graphics::gptn: Coordinate -207.932 + 1.39227\\[ImaginaryI] in {22,
-207.932 \
+ 1.39227\\[ImaginaryI]} is not a floating-point number.

The other 99 results make a nice plot.

• Follow-Ups:
  • Re: FindRoot anomaly (example from Mathematica Tutorial)
    • From: gardyloo <gardyloo@mail.wsu.edu>