Recent changes to 2458: to_poly_solve gives a wrong solution for cos(x)=sin(3x)http://sourceforge.net/p/maxima/bugs/2458/2012-08-16T00:46:34Zto_poly_solve gives a wrong solution for cos(x)=sin(3x)2012-08-16T00:46:34Z2012-08-16T00:46:34ZJean-Yveshttp://sourceforge.net/u/jyoberle/http://sourceforge.netcac26016a99289c958f6128616359cba7d25c277Hi,
When doing:
load\(to\_poly\_solve\);
algexact:true;
to\_poly\_solve\(cos\(x\)-sin\(3\*x\),x\);
I get:
to\_poly\_solve: to\_poly\_solver.mac is obsolete; I'm loading to\_poly\_solve.mac instead.
%union\(\[x=-\(4\*%pi\*%z0+%pi\)/4\],\[x=\(4\*%pi\*%z1+%pi\)/8\]\)
But I think that the first solution should be \(based on hand solving\): \(4\*%pi\*%z0+%pi\)/4 \(no minus sign\).
For example: if we consider %z0 = 0 in the to\_poly\_solve solution, we get x=-%pi/4 which is not a solution of the equation cos\(x\)-sin\(3\*x\). On the other hand, if we set %z0 = 0 in the hand found solution, we get x=%pi/4 which is a solution.
The build\_info is: build\_info\("5.27.0","2012-05-08 11:27:57","i686-pc-mingw32","GNU Common Lisp \(GCL\)","GCL 2.6.8"\).
Best regards,
Jean-Yves