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newbie problem with NIntegrate

• To: mathgroup at smc.vnet.net
• Subject: [mg49791] newbie problem with NIntegrate
• From: "Xiaoxun" <dbjunxiao at hotmail.com>
• Date: Sun, 1 Aug 2004 04:09:54 -0400 (EDT)
• Organization: The Chinese University of Hong Kong
• Sender: owner-wri-mathgroup at wolfram.com

Hi, all,

Please advices:

Geom = (200 >=x>= 100 && 50 >= y >= -50 && -20 <= z <= 20);
gr[x_, y_, z_] := 2 /; Geom;
gr[x_, y_, z_] := 0 /; ! (Geom);
N[Integrate[gr[x, y, z], {x, 0, 300}, {y, -100, 100}, {z, -30, 30}]
This gives a result of 799995.
However, if changing the x range to {x,0,600} results 799993.
                                and {x,0,900} results 0;

So what could we do to ensure the right answer?

• Follow-Ups:
  • Re: newbie problem with NIntegrate
    • From: DrBob <drbob@bigfoot.com>