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RE: Bug in math4

  • To: mathgroup at smc.vnet.net
  • Subject: [mg20662] RE: [mg20633] Bug in math4
  • From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
  • Date: Sun, 7 Nov 1999 02:10:01 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

Lennart Bengtsson indicated the problem discussed earlier might be at
x=Pi/2.  Below we see this is the case. I don't know I didn't make the
connection between 1.57... and Pi/2 earlier.


In[1]:=
Integrate[Sqrt[2-Sin[x]],{x,1,4}]

Out[1]=  (*** Wrong answer ***)
-2*EllipticE[(-4 + Pi/2)/2, -2] + 
 2*EllipticE[(-1 + Pi/2)/2, -2] + 
 4*EllipticF[I*ArcSinh[1/Sqrt[2]], -2]


In[2]:=
Integrate[Sqrt[2-Sin[x]],{x,1,Pi/2,4}]

Out[2]=   (*** Right answer ***)
-2*EllipticE[(-4 + Pi/2)/2, -2] + 
2*EllipticE[(-1 + Pi/2)/2, -2]

--------------------
Regards,
Ted Ersek

For Mathematica tips, tricks see 
http://www.dot.net.au/~elisha/ersek/Tricks.html


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