Fourier series, is this valid?

Trevorman
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Hi, I have a Fourier problem that i do not know if it is valid to do the calculations like this.

The Fourier transform looks like this
##
\hat{v}(x,\omega) = \frac{\hat{F}(\omega)}{4(EI)^{\frac{1}{4}}i \omega^{\frac{3}{2}}(\rho A)^{\frac{3}{4}}}\left[ e^{-i\left[\omega^2 \frac{\rho A}{EI} \right]^{\frac{1}{4}}x} -ie^{-\left[\omega^2 \frac{\rho A}{EI} \right]^{\frac{1}{4}}x} \right]##

and is the Fourier transform of a displacement for a wave in a beam.
The inverse Fourier transform of this equation is the displacement and is displayed below

##v(x,t)= \sum_n\hat{v} \cdot e^{i\omega t}##

What I want to calculate is the x derivative of ##v(x,t)##. Is it valid to calculate ##\frac{\partial \hat{v}}{\partial x}## and do a inverse Fourier transform to get ##v^\prime(x,t)##

In other words, is this valid
## v^\prime(x,t) = \sum_n \hat{v}^\prime \cdot e^{i \omega t}##
 
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I don't see any problem with what you wrote.
 
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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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