Revision as of 21:54, 22 April 2018

Table of CT Fourier Series Coefficients and Properties

Function	Fourier Series	Coefficients

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Property Name	Property	Proof
Linearity	$\mathfrak{F}(c_1g(t) + c_2h(t) = c_1G(f) + c_2H(f)$	$\mathfrak{F}(c_1g(t) + c_2h(t) = \int_{-\infty}^\infty c_1g(t) dt + \int_{-\infty}^\infty c_2h(t) dt$ $=c_1\int_{-\infty}^\infty g(t)e^{i2\pi ft} dt + c_2 \int_{-\infty}^\infty g(t)e^{i2\pi ft} dt$ $$ =c_1G(f) + c_2H(f) $$
Time Shifting	$\mathfrak{F}(g(t - a)) = e^{-i2\pi fa}*G(f)$	$\mathfrak{F}(g(t - a)) = \int_{-\infty}^\infty g(t-a)e^{-2\pi ft}dt$ $=\int_{-\infty}^\infty g(u)e^{-i2\pi f(u+a)}du$ $=e^{-i2\pi fa}\int_{-\infty}^\infty g(u)e^{-i2\pi fu}du$ $=e^{-i2\pi fa} G(f)$
Time Scaling	$\mathfrak{F}(g(ct)) = \frac{G(\frac{f}{c})}{\|c\|}$	$\mathfrak{F}(g(ct)) = \int_{-\infty}^\infty g(ct)e^{-i2\pi ft}dt$ subtitute : u = ct, du = cdt $\mathfrak{F}(g(ct)) = \int_{-c\infty}^{c\infty} \frac{g(u)}{c}e^{-i2\pi f\frac{u}{c}}du$ if c is greater than 0: then no signs change. if c is less than 0: the integration must be flipped as well as the negative from the c so you still get the same equation. therefore the absolute value of c is obtained.

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 if c is less than 0: the integration must be flipped as well as the negative from the c so you still get the same equation. therefore the absolute value of c is obtained.
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