Differentiation
Define a function x(t) with its Fourier transform being X(jw)
Then by definition x(t) = $ \int\limits_{-\infty}^{\infty}X(jw)e^{(-\jmath wt)}dt $
The derivative of x(t) equals
= $ \int\limits_{-\infty}^{\infty}jwX(jw)e^{(-\jmath wt)}dt $
With the key point being made that differentiation and integration are interchangable operations. The proof of this is not
difficult however it is time consuming. The book assumes that summations and integrations can be interchange also,
therefore I will go without proof of the interchangability of differentiation and integration.
so Fx(t)' = jwX(jw)
