matlab,fft,noise,spectrum,mathcad

The main reason why it doesn't work is due to the scaling factor of the FFT between MathCad and MATLAB. With MathCad, there is an extra scaling factor of 1/sqrt(N) whereas MATLAB does not include this said scaling factor. As such, you'll need to multiply your FFT results by this...

I'm using Mathcad 15--- I can insert a derivative using the Calculus palette, and then right-click on the derivative. Choose View Derivative As > Partial Derivative on the popup menu....