Upgrading from:

Calculus`FourierTransform`

The symbolic functions in Calculus`FourierTransform` have been added to the built-in Mathematica kernel.
The numerical functionality in Calculus`FourierTransform` is now available through the newly created Fourier Series Package.

To access functionality from the new Fourier Series Package, load FourierSeries`:

Version 5.2

This gives a numerical approximation to the Fourier transform of Exp(-t²)/(1+t) with respect to at :

Version 5.2