elimination (substitution) of sum of expresions

[jiribol]

Hello comunity, I would appreciate a help with following. I am triing to substitute iid(t), iiq(t) for iia(t), iib(t), iic(t) in equation:

'diff(iid(t),t,1)=(-2Lfwiic(t)sin((3wt+2*%pi)/3)+2*(vic(t)-vcfc(t)+Rfigc(t))cos((3wt+2*%pi)/3)-2*(Ri+Rf)iic(t)cos((3wt+2*%pi)/3)-2Lfwiib(t)sin((3wt-2*%pi)/3)+2*(vib(t)-vcfb(t)+Rfigb(t))cos((3wt-2*%pi)/3)-2*(Ri+Rf)iib(t)cos((3wt-2*%pi)/3)-2Lfwiia(t)sin(wt)+2(via(t)-vcfa(t)+Rfiga(t))cos(wt)-2(Ri+Rf)iia(t)cos(wt))/(3Lf),

where:
iid(t)=(2iic(t)cos(wt+(2%pi)/3))/3+(2iib(t)cos(wt-(2%pi)/3))/3+(2*iia(t)cos(wt))/3;

iiq(t)=-(2iic(t)sin(wt+(2%pi)/3))/3-(2iib(t)sin(wt-(2%pi)/3))/3-(2*iia(t)sin(wt))/3

( trying to eliminate iia(t), iib(t), iic(t) and have iid(t), iiq(t) instead of)

So far I have tried subst, ratsubst, fullratsubst, eliminate, let/letsimp, but all failed :(.

Looking forward for your hints, Jiri.

[jiribol]

above solved. It looks it is related to sin and cos. When cos and sin substituted with a f(t), fullratsubst works well to eliminate iia(t), iib(t) and iic(t).