# FourierParameters causing function not to simplify

When evaluating this expression, Mathematica simplifies the result:

FourierTransform[FourierTransform[u[t], t, s], s, t]


This simplifies to u[-t], as expected.

But let's say I want this expression using different Fourier parameters.

FourierTransform[
FourierTransform[u[t], t, s, FourierParameters -> {1, - 1}],
s, t, FourierParameters -> {1, -1}
] // FullSimplify


When evaluating this, Mathematica leaves the result unaltered, with or without FullSimplify. The result should be $2\pi\ u(-t)$. Is it possible to get this result, or a similar result using these parameters? I would like to test these kinds of expressions with Mathematica, but without the right parameters it is kind of useless.

I would suggest reporting the unevaluated FourierTransform[] with explicitly-set FourierParameters to support.
SetOptions[FourierTransform, FourierParameters -> {1, -1}];

• I sent a report with this problem. The suggested fix is actually what I want since it saves you from typing FourierParameters -> ... over and over. I have never heard of SetOptions but it seems a really useful function. – user3502079 Nov 4 '17 at 19:32