#5241 Risch integrator drops algebraic unit from a denominator

[David Scherfgen]

(%i1) f: x*sin(x)*log(sin(x)+1)$
(%i2) risch(f, x);
(%o2) ((sin(x)-x*cos(x))*log(sin(2*x)^2+4*cos(x)*sin(2*x)+cos(2*x)^2
                                        +(-(4*sin(x))-2)*cos(2*x)+4*sin(x)^2
                                        +4*sin(x)+4*cos(x)^2+1)
 +(2*%i*sin(x)-2*%i*x*cos(x))*atan2(-cos(2*x)+2*sin(x)+1,sin(2*x)+2*cos(x))
 +2*log(sin(x)^2+2*sin(x)+cos(x)^2+1)+4*%i*atan2(sin(x)+1,cos(x))
 +(-(%i*x^2)-log(2)*x-%i*log(2)-2*%i)*sin(x)
 +(-x^2+%i*log(2)*x-log(2)-2)*cos(x)+x^2-2*%i*x)
 (%i3) ratsimp(exponentialize(diff(%, x) - f));
 (%o3) /* some long expression definitely non-zero */

Detected by Claude.

[David Scherfgen]

Fixed by commit [0ca8a1].