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Re: Re: Bug of Integrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83036] Re: [mg83019] Re: Bug of Integrate
  • From: "Misco Viadas" <misvrne at gmail.com>
  • Date: Thu, 8 Nov 2007 06:10:16 -0500 (EST)
  • References: <fg4dfv$6c3$1@smc.vnet.net> <fg6pse$d44$1@smc.vnet.net>

These are my results:

$Version
5.2 for Microsoft Windows (June 20, 2005)

x[t_]:=a Cos[t];y[t_]:=a Sin[t];

The length of the semicircunference is:

In[]: Integrate[Sqrt[1+(y'[t]/x'[t])^2)]*x'[t],{t,0,Pi}]
Out[]: -a*Pi

The length total is:
In[]: Integrate[Sqrt[1+(y'[t]/x'[t])^2)]*x'[t],{t,0,2Pi}]
Out[]: 2*a*Pi


$Version
6.0 for Microsoft Windows (32-bit) (June 19, 2007)

x[t_]:=a Cos[t];y[t_]:=a Sin[t];


The length of the semicircunference is:

In[]: Integrate[Sqrt[1+(y'[t]/x'[t])^2)]*x'[t],{t,0,Pi}]
Out[]: -a*Pi

The length total is:


In[]: Integrate[Sqrt[1+(y'[t]/x'[t])^2)]*x'[t],{t,0,2Pi}]
Out[]: 0
All my calculations  stored in my computer are false?. I have to review
them. It means that 3000 manhours to the sea.



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