Fourier Transfer of sawtooth function

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The discussion focuses on calculating the Fourier transform of the function h(t) = t over the interval [0, 1]. The Fourier transform is expressed as H(s) = ∫01 h(t) e-i 2 π f t dt, leading to a series of transformations and simplifications. The final expression for H(s) is derived as H(s) = (1/ω2) [(iω + 1)e-iω - 1]. Participants confirm the correctness of the calculations, indicating no errors in the approach taken by the original poster.

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Homework Statement


Find the magnitude and phase of the Fourier transform of h(t)=t over the interval 0,1

Homework Equations


H(s) = \int^{1}_{0} h(t) e^{-i 2 \pi f t} dt

The Attempt at a Solution


I found this thread: https://www.physicsforums.com/threads/fourier-transform-of-the-sawtooth-function.502113/ but can't seem to come close to the same result. Letting a = -i 2 \pi f = -i \omega we get:
##H(s) = \int^{1}_{0} t e^{a t} dt \\
= \frac{e^{at}}{a^2}(at-1)|^{1}_{0} \\
= \frac{1}{a^2} \left( a t e^{at} - e^{at}\right)|^{1}_{0} \\
= \frac{1}{a^2}(ae^{a} - e^{a} + 1) \\
= \frac{1}{a^2}\left[(a-1) e^{a} + 1 \right] \\
= \frac{1}{a^2}(ae^{a} - e^{a} + 1) \\
= \frac{1}{(-i \omega)^2}\left[(-i \omega-1) e^{-i \omega} + 1 \right] \\
= \frac{-1}{\omega^2}\left[(-i \omega-1) e^{-i \omega} + 1 \right] \\
= \frac{1}{\omega^2}\left[(i \omega+1) e^{-i \omega} - 1 \right] \\
= \frac{1}{\omega^2}\left[(i \omega+1) (\cos \omega - i \sin \omega) - 1 \right] \\
\vdots \\
= \frac{1}{\omega^2} \left[ i (\omega\cos\omega-\sin \omega) + (\omega \sin \omega + \cos \omega -1)\right]##
I just don't see how this is converging to the solution in the referenced thread. Have I gone wrong somewhere?
 
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hotvette said:

Homework Statement


Find the magnitude and phase of the Fourier transform of h(t)=t over the interval 0,1

Homework Equations


H(s) = \int^{1}_{0} h(t) e^{-i 2 \pi f t} dt

The Attempt at a Solution


I found this thread: https://www.physicsforums.com/threads/fourier-transform-of-the-sawtooth-function.502113/ but can't seem to come close to the same result. Letting a = -i 2 \pi f = -i \omega we get:
##H(s) = \int^{1}_{0} t e^{a t} dt \\
= \frac{e^{at}}{a^2}(at-1)|^{1}_{0} \\
= \frac{1}{a^2} \left( a t e^{at} - e^{at}\right)|^{1}_{0} \\
= \frac{1}{a^2}(ae^{a} - e^{a} + 1) \\
= \frac{1}{a^2}\left[(a-1) e^{a} + 1 \right] \\
= \frac{1}{a^2}(ae^{a} - e^{a} + 1) \\
= \frac{1}{(-i \omega)^2}\left[(-i \omega-1) e^{-i \omega} + 1 \right] \\
= \frac{-1}{\omega^2}\left[(-i \omega-1) e^{-i \omega} + 1 \right] \\
= \frac{1}{\omega^2}\left[(i \omega+1) e^{-i \omega} - 1 \right] \\
= \frac{1}{\omega^2}\left[(i \omega+1) (\cos \omega - i \sin \omega) - 1 \right] \\
\vdots \\
= \frac{1}{\omega^2} \left[ i (\omega\cos\omega-\sin \omega) + (\omega \sin \omega + \cos \omega -1)\right]##
I just don't see how this is converging to the solution in the referenced thread. Have I gone wrong somewhere?

Your answer is correct; you have not gone wrong anywhere that I can see.
 

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