INTEGRATING ROUNDING FUNCTIONS-(I)

22 03 2009


Integer Rounding Functions can be found in many Number Theory texts, but I wasn´t able to find something about its integrals.

The following expresions can be derived just from their plots, adding and substracting areas. They hold if \displaystyle \;x\geq 0

The Triangular Numbers function is used to get shorter expresions.

\displaystyle T(n)=\frac{n^{2}+n}{2}

FLOOR FUNCTION DEFINITE INTEGRAL:

\displaystyle \int_0^x \lfloor x \rfloor dx = \left\{{x}\right\}\lfloor x \rfloor +T(\lfloor x \rfloor-1)

FRACTIONAL PART FUNCTION DEFINITE INTEGRAL:

\displaystyle \int_0^x \left\{{x}\right\} dx = \frac{x}{2}- \left\{{x}\right\} +T( \left\{{x}\right\} )

\displaystyle \int_0^x \left\{{x}\right\} dx = \frac{x}{2} +T( \left\{{x}\right\}-1 )

\displaystyle \int_0^x \left\{{x}\right\} dx =\frac{x+ \left\{{x}\right\}^{2}-\left\{{x}\right\}}{2}

CEILING FUNCTION DEFINITE INTEGRAL:

\displaystyle \int_0^x \lceil x \rceil dx = \lceil x \rceil (x-\lceil x \rceil)+T(\lceil x \rceil)

All these formulas can be changed using the relations between them:

\displaystyle \left\{{x}\right\}=x- \lfloor x \rfloor

This topic doesn´t finish here it´s going to be used on incoming posts.


Archives:

[a]-032209-INTEGRATING INTEGER ROUNDING FUNCTIONS-(I).nb
[b]-032309-CheckIntegratingIntegerRoundingFunctions.pdf


References:


[1]-Štefan Porubský:Retrieved 2009/3/22 from Interactive Information Portal for Algorithmic Mathematics, Institute of Computer Science of the Czech Academy of Sciences, Prague, Czech Republic http://www.cs.cas.cz/portal/AlgoMath/NumberTheory/ArithmeticFunctions/IntegerRoundingFunctions.htm
[2]-Greg Gamble: The University of Western Australia SCHOOL OF MATHEMATICS & STATISTICS The Floor or Integer Part function

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