Question: Issues with differential and D operator

Hi,

I am trying to do a numerical approximate method 'method of multiple scales'. And in doing so I am getting following equation.

restart

junk := -n*v_SDD*x[1](T[0], T[1], T[2])+x[1](T[0], T[1], T[2])+(D[1, 1](x[1]))(T[0], T[1], T[2])+2*kappa*(D[1](x[1]))(T[0], T[1], T[2])+n*v_SDD*x[1](T[0]-tau_1, T[1], T[2])-psi*n*x[1](T[0]-tau_1, T[1], T[2])+psi*n*x[1](T[0], T[1], T[2])

-n*v_SDD*x[1](T[0], T[1], T[2])+x[1](T[0], T[1], T[2])+(D[1, 1](x[1]))(T[0], T[1], T[2])+2*kappa*(D[1](x[1]))(T[0], T[1], T[2])+n*v_SDD*x[1](T[0]-tau_1, T[1], T[2])-psi*n*x[1](T[0]-tau_1, T[1], T[2])+psi*n*x[1](T[0], T[1], T[2])

(1)

evalf(subs(x[1](T[0], T[1], T[2]) = R(T[1], T[2])*sin(omega*T[0]+phi(T[1], T[2])), %))

-1.*n*v_SDD*R(T[1], T[2])*sin(omega*T[0]+phi(T[1], T[2]))+R(T[1], T[2])*sin(omega*T[0]+phi(T[1], T[2]))+(D[1, 1](x[1]))(T[0], T[1], T[2])+2.*kappa*(D[1](x[1]))(T[0], T[1], T[2])+n*v_SDD*x[1](T[0]-tau_1, T[1], T[2])-1.*psi*n*x[1](T[0]-tau_1, T[1], T[2])+psi*n*R(T[1], T[2])*sin(omega*T[0]+phi(T[1], T[2]))

(2)

``


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Now I need to substitute x_1(T0,T1,T2)=R(T1,T2)sin(omega*T0+phi(T1,T2)) in the expression and evaluate it.  But on substituting, it is not solving for the 'D' operator. In a similar line if I will have a differential term like

D1(x1)(T0-tau_1,T1,T2) and I have to substitute x1(T0-tau_1,T1,T2) then how can i do it?

Please help me regarding it.

Thanks and regards

Sunit

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