I came across this curious problem today: trigsimp gives "Simplification recursion too deep" errors trying to simplify 1-sin^2(x), for some choices of x.

CSL was coded by Codemist Ltd, 1988-2008

Distributed under the Modified BSD License

REDUCE, 15-Sep-08 ...

1: 1-(sin(pi*x/2))**2;

2: trigsimp(ws);

***** sub

3: trigsimp(ws,cos);

***** Simplification recursion too deep

***** Invalid simplification

Oh dear. A similar exercise with x instead of pi*x/2 was OK:

CSL was coded by Codemist Ltd, 1988-2008

Distributed under the Modified BSD License

REDUCE, 15-Sep-08 ...

1: 1-(sin(x))**2;

2: trigsimp(ws);

3: trigsimp(ws,cos);

cos(x)

I've tried a few other choices for x in the above (e.g., x*y, x/y, pi*x) and they are all OK -- it is only pi*x/2 that I've found that gives this problem.

Many thanks for any help!

Alastair Rucklidge