Wednesday, September 2, 2015

calculus - Why does fracsinxx have no anti-derivative

I've been messing around with indefinite integrals. Watching some youtube videos and I found the Sinc function and that it has no finite Anti-derivative.
Desmos being my favourite program ever I decided to graph to the equations
y=sin(x)x and y=x0sin(a)ada (only way I could do indefinite integrals in Desmos)



If you do this you might notice y=sin(x)x looks very similar to y=sinh(x) and y=x0sin(a)ada looks very similar to y=arctan(x)



I wondered how we know that sin(x)x has no finite anti-derivative because these simple functions give seemingly accurate approximations



Best approximation I could get for it in the short time I had was:
sinh(x)ddx[sin(x)x]π2

or
2arctan(ex)+sin(x)x2cos(x)xπ2
(In all the examples I'm assume C=0 because it's not important and I'm assuming any points with 00 evaluate to their limits as x tends to 0)

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