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Weierstrass function

In mathematics, the Weierstrass function was the first example found of a kind of function with the property that it is continuous everywhere but differentiable nowhere. Almost all continuous functions are nowhere differentiable, and this property is both stable and generic. Weierstrass functions are defined by

f(x)=\sum_{n=0}^\infty a^n\cos(b^n\pi x),

where 0 < a < 1 and

ab>1+\frac{3}{2}\pi.

The following graphs display the function f(x)=\sum_{n=0}^\infty (1/2)^n\cos(20^n\pi x),

(Note: These graphs do not correctly display the function, they display only a subsampled version of this function.)

Image:Weierfunc1.gif Image:Weierfunc2.gif

See also

Last updated: 10-24-2005 04:58:34
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