Computation of FFT

Questions
1

I have the following differential equation.

sols = NDSolve[{x'[t] == (1/4) x[t - 15]/(1 + x[t - 15]^10) - x[t]/10, x[t /; t <= 0] == 0.01}, x, {t, 0, 10}];

How can I compute FFT of x’[t] or x[t].

2

NDSolve returns an interpolation. For FFT, you need a list of points.

You can use Table to create a list of points:

Table[myFunction[t],{t,0,10,0.1}]

For examples of doing FFT, see the documentation for Fourier.

3

Thank you