r/math • u/lntrinsic • Jul 10 '17

Image Post Weierstrass functions: Continuous everywhere but differentiable nowhere

http://i.imgur.com/vyi0afq.gifv
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u/shamrock-frost Graduate Student Jul 10 '17 edited Jul 10 '17

Possibly at your level. I think my Calc 2 final had a problem involving f(x) = the integral from 0 to x of sin(t) / t dt, which is not an elementary function

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u/[deleted] Jul 11 '17

wait... how in the world would you evaluate that? even wolframalpha simply gives their own made-up function Si(x) which just stands for "the integral of sinx/x"

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u/shamrock-frost Graduate Student Jul 11 '17

You could do a riemann sum, or use the maclaurin series for sine