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MathGroup Archive 2000

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Re: A strange bug in Solve

  • To: mathgroup at
  • Subject: [mg24482] Re: A strange bug in Solve
  • From: Warren Wolfe <"75127,1531">
  • Date: Wed, 19 Jul 2000 01:21:55 -0400 (EDT)
  • References: <8k9iar$>
  • Sender: owner-wri-mathgroup at

Andrzej Kozlowski wrote:

> I have long ago learned to be careful when making claims about kernel bugs
> in Mathematica, but this time I am pretty sure I have found a fairly serious
> one, even though it looks rather strange.
> I asked Mathematica to solve a system of two trigonometric equations:
> In[1]:=
> eqns = {2*Cos[2*t]*Cos[u/2] + Cos[t]*Sin[u/2] == 0,
>     (Cos[u/2]*Sin[t])/2 - (Sin[2*t]*Sin[u/2])/2 == 0};
> To my surprise Solve returned the empty list (I knew these equations do have
> solutions for geometric reasons):
> In[2]:=
> Solve[eqns, {u, t}]
> Out[2]=
> {}

When I tried this problem using Mathematica 3.0 for Windows it found 8 solutions
and also gave the Solve::ifun message. There was no need for Simplify.

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