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MathGroup Archive 1990

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Integrate?

  • To: <mathgroup at yoda.ncsa.uiuc.edu>
  • Subject: Integrate?
  • From: Harald Hanche-Olsen <hanche at imf.unit.no>
  • Date: Fri, 2 Nov 90 18:21:48 +0100

Robert Staerk <staerk at iam.unibe.ch> writes ...

   Mathematica gives a wrong answer to the following integral:

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

   Is this a known bug?

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

   Out[1]= 0

This is apparently caused by Mathematicas attempts at being clever
about things like complex square roots, branch cuts and the like.
Yes, it is known.  And some people think Mathematica is brain-dead
because of it.  Myself, I haven't decided yet.  I keep alternating
between Mathematica and Maple, just like you seem to do...

- Harald Hanche-Olsen <hanche at imf.unit.no>
  Division of Mathematical Sciences
  The Norwegian Institute of Technology
  N-7034 Trondheim, NORWAY


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