How simplify ex ?
(%i1) ex:sin(x+(1907*%pi)/89)+cos(x-(13*%pi)/178)$
(%i2) simp(e):=block([r,partswitch],partswitch:true,
r:part(e,2,1,2),
subst(x=t-r,e),
subst(t=r+x,%%))$
(%i3) simp(ex);
(%o3) 0
For other expresinions "simp" does nothing
(%i4) simp(sin(x+a)+cos(x-b));
(%o4) cos(x-b)+sin(x+a)
(%i5) simp(sin(x)+cos(x-(13*%pi)/178));
(%o5) cos(x-(13*%pi)/178)+sin(x)
best
Aleksas D