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Re: Not all points plot on my graph...

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105209] Re: Not all points plot on my graph...
  • From: David Bailey <dave at removedbailey.co.uk>
  • Date: Tue, 24 Nov 2009 05:50:13 -0500 (EST)
  • References: <hedte4$lsn$1@smc.vnet.net>

davef wrote:
> Why is it when I write this...
> 
> Clear[f, x]
> f[x_] = (x + 2)^(2/3)
> Plot[f[x], {x, -3, 0}, PlotRange -> {{-3, 0}, {-4, 4}}]
> f[-3]
> 
> .. I get no values show in the graph for x<-2 even though f[-3]
> evaluates to (-1)^(2/3).
> 
> (-1)^(2/3) evaluates as f[-3]=1 so why wouldn't the point (-3,1) plot
> on my graph?
> 
> 
(-1)^(2/3) is a complex number, so you can't plot it on a real plot. 
Have a look at:

  (-1)^(2/3)//N

and you will see your mistake.

David Bailey
http://www.dbaileyconsultancy.co.uk


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