A straight line (y=x) can be written as a sum over sinusoids, known as a Fourier Series.pic.twitter.com/Obii1qd62T
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Replying to @InertialObservr @DynamicsSIAM
No, you only get y=x in (-pi,pi), as you’ve drawn, and then extended periodically from there (since every function in the series is 2pi periodic). The dual of the line is the line, so you’d need an integral to recover the actual line. Presumably you know this, so why fib?...
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Replying to @AlexKontorovich @DynamicsSIAM
that's right, it converges to y=x in (-π,π) for the Fourier series (as opposed to the transform). Given that it does converge to a line on (-π,π), i wouldn't say i fibbed.. This is twitter,not an academic conference.The purpose of my tweets is to get across the basic idea in..
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But ... isn't the "basic idea" that one can use a Fourier series to approximate any periodic signal? So why start with a "straight line", an inherently aperiodic object? Also, sorry for the nitpick, but it doesn't converge to y=x in (-π,π). The integral error converges to zero.
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lines are precisely what sawtooth waves are..
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Respectfully no. They're line segments. A sawtooth wave is piecewise linear, not linear.
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You can see from the boundary conditions that this gif precisely corresponds to a sawtooth wave with period 2 pi
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Your OP literally says "a straight line (y=x)". No boundary conditions mentioned. No indication in the GIF that the signal is periodic. I've spent five years teaching this stuff to people with mostly no math/science background and I'm telling you your tweet is misleading.
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Replying to @oe1cxw @InertialObservr and
Btw, the easiest way to graphically indicate a period is of course to show more than one period of the signal. See for example how I show a little more than a period in http://svn.clifford.at/tools/trunk/electrotools/dftdemo.html … and https://www.youtube.com/watch?v=AjlHBx0zV7c ….
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