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MathGroup Archive 1990

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Integrate?

  • To: <mathgroup at yoda.ncsa.uiuc.edu>
  • Subject: Integrate?
  • From: Robert Staerk <staerk at iam.unibe.ch>
  • Date: 31 Oct 90 13:41 +0100

Mathematica gives a wrong answer to the following integral:

                            2 Pi
                             /
                            |                  1/2
                            |    (2 - 2 cos(x))    dx
                            |
                           /
                           0

Is this a known bug?

idefix> math
Mathematica (sun4) 1.2 (August 22, 1989) [With pre-loaded data]
by S. Wolfram, D. Grayson, R. Maeder, H. Cejtin,
   S. Omohundro, D. Ballman and J. Keiper
with I. Rivin and D. Withoff
Copyright 1988,1989 Wolfram Research Inc.
 -- Terminal graphics initialized -- 

In[1]:= Integrate[ Sqrt[2 - 2 Cos[x]], {x, 0, 2 Pi}]

Out[1]= 0

In[2]:= NIntegrate[ Sqrt[2 - 2 Cos[x]], {x, 0, 2 Pi}]

Out[2]= 8.

In[3]:= Quit
idefix> maple
    |\^/|      MAPLE V
._|\|   |/|_.  Copyright (c) 1981-1990 by the University of Waterloo.
 \  MAPLE  /   All rights reserved.  MAPLE is a registered trademark of
 <____ ____>   Waterloo Maple Software.
      |        Type ? for help.
> int( sqrt(2 - 2 * cos(x)), x=0...2*Pi );

                                       8

> done
bytes used=1447572, alloc=917336, time=8.116
idefix>

-------------------------------------------------------------------------
Robert Staerk (St\"ark)   | Laenggassstrasse 51 | Phone: +41 31 65 85 58
Institut fuer Informatik  | CH-3012 Bern        | Fax:   +41 31 65 39 65
und angewandte Mathematik | Switzerland         | <staerk at iam.unibe.ch>
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