@Mariusz Iwaniuk 

Can it be convert(solution, [sin(t),cos(t),Bessel(t)])

I would like the solution mixed with three special functions. can it be this ?

@Mariusz Iwaniuk 

Differential system is confidential

But it is unique solution

It is usually in terms of Exponential function

So I ask how to dsolve to solution in terms of other special functions

You can tell me the steps that I can try myself.

I find reduce_order and ...gen example

But the example can not be searched again

I do not whether this can help