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DSolve bug: addendum to previous posting

• To: mathgroup at yoda.physics.unc.edu
• Subject: DSolve bug: addendum to previous posting
• From: <Constantin.Kahn at cdc2.c.mathematik.uni-hannover.dbp.de>
• Date: 17 Feb 92 10:40

Hi, one person claimed that my posting about a bug in DSolve which caused it
to return wrong explicit solutions for the system of differential equations
   a'[t] - Cos[t] b[t] == 0  &&  b'[t] + Cos[t] a[t] == 0
was easily misunderstood. I did not intend to say that the auxiliary functions
A[t] and B[t] were solutions. Of course they aren't. They are equal to the
"solutions" returned by Mathematica. I introduced them to show that in this
particular case Simplify doesn't perform up to its name. Besides, there are
valid explicit solutions satisfying a[0] == 0 && b[0] == 1 given by
   a[t] = Sin[Sin[t]]  and  b[t] = Cos[Sin[t]].

Regards, Constantin Kahn