# Bug in Solve (Mathematica 9)

The issue seems to be fixed as of Version 10.1.

Just came across the strangest bug under both Mathematica 9.0.0 and 9.0.1. If one enters:

Solve[m == p Sin[x] && -Pi/2 < x < Pi/2, x]


... then Mathematica whirrs and whirrs (running on my Mac Pro with OS X 10.6.8), and doesn't seem to produce any answer (I gave up after a few minutes). But if one changes symbol p to something that 'sorts' earlier than an m, such as an 'a' or 'b', then it works correctly:

Solve[m == b Sin[x] && -Pi/2 < x < Pi/2, x]


Solve::nsmet: This system cannot be solved with the methods available to Solve.

Obviously, one can add assumptions on p or b to make it solve, but that is not the issue being raised.

Is this just a Mac issue, or are others experiencing the same on other platforms?

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Ah, I've seen this one before... I remember an answer/comment from Daniel saying that this was a hashing problem and cannot be fully fixed, but they address specific and common cases as they encounter them. –  The Toad Feb 8 '13 at 19:04
Here's the post I was thinking of: stackoverflow.com/q/5402214 –  The Toad Feb 8 '13 at 19:06
Different issue. The hashing one only causes a slowdown in dealing with large, deep expressions. Will investigate. –  Daniel Lichtblau Feb 8 '13 at 19:54
Reported as a bug. –  Daniel Lichtblau Feb 8 '13 at 20:03
FWIW: same behavior in Windows version (Mathematica 9.0.0.0 under Windows 7) –  stevenvh Feb 9 '13 at 10:58