I have a horrible expression:
phi:
((c-1)*cos(x)*sin((c+1)*x)+(1-c)*sin(x)*cos((c+1)*x)
+ (-c-1)*cos(x)*sin((c-1)*x)
+(-c-1)*sin(x)*cos((c-1)*x)) /(2*c^2-2);
which can be simplified to -sin(c*x)/(c^2-1)
I simplified it by hand using a number of sin(a+b)=sin(a)cos(b)+sin(b)cos(a)
and cos(a+b) rules using subst(). But can it be simplified in an automatic way
without visual inspection?
Best,
Nijso