Solve symbolic equation with derivatives

I want to solve an equation with the symbolic math toolbox. This equation also contains derivatives. E.g.:

eqn1 = 0 == x + y + diff(f(t),t)
sol1 = solve(eqn1, diff(f(t),t));

But I always get an empty structure as solution. Is there any way to do this or do I have to convert the diff(f(t),t) into another symbolic variable and convert it back to the derivative after I solved the equation?

Answer 1

[Steradiant]

isolate(eqn,expr)

is the function I was looking for.

Answer 2

[madhan ravi]

dsolve(...) is the one to be used for odes.

[Steradiant]

I acutally don't want to solve the ode as is, I want to solve the equation in a way, that I can reuse it in another equation. Meaning, that I express x from eqn1 and enter x into eqn2 and so on. After some steps I have the ode which I can possibly solve.

[madhan ravi]

syms x y df
% df -> diff(f(t),t)
eqn1 = 0 == x + y + df
sol1 = solve(eqn1, df)
doc subs

[Steradiant]

Yeah, this is the workaround I was thinkin of but I'd have prefered a built in way rather than defining loads of symbolics.

[madhan ravi]

Good luck.