Difference between revisions of "Thomae function"
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[http://math.stackexchange.com/questions/530097/proof-of-continuity-of-thomae-function-at-irrationals]<br /> | [http://math.stackexchange.com/questions/530097/proof-of-continuity-of-thomae-function-at-irrationals]<br /> | ||
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Revision as of 18:29, 24 May 2016
Thomae's function (sometimes called the popcorn function, raindrop function, Stars over Babylon) is given by the formula $$f(x) =\begin{cases} 1 & \text{if } x= 0 \\ \tfrac1{q} & \text{if } x = \tfrac{p}{q}\\ 0 & \text{if } x \in \mathbb{R}-\mathbb{Q}. \end{cases}$$
Plot of the Thomae function.
Contents
Properties
Theorem: The Thomae function is continuous at all irrational numbers and discontinuous at all rational numbers.
Proof: █
Theorem: The Thomae function has a (strict) local maximum at each rational number.
Proof: █
Theorem: The Thomae function $f(x)$ is Riemann integrable and $$\displaystyle\int_0^1 f(x) dx = 0.$$
Proof: █
Videos
Thomae Function by Douglas Harder
Thomae Function by Bret Benesh
See also
Modifications of Thomae's Function and Differentiability
