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Issue No. 02 - February (2009 vol. 58)
ISSN: 0018-9340
pp: 226-237
Marc Daumas , ELIAUS, UPVD, Perpignan
David Lester , University of Manchester, Manchester
Céar Muñoz , National Institute of Aerospace, Hampton
Real number calculations on elementary functions are remarkably difficult to handle in mechanical proofs. In this paper, we show how these calculations can be performed within a theorem prover or proof assistant in a convenient and highly automated as well as interactive way. First, we formally establish upper and lower bounds for elementary functions. Then, based on these bounds, we develop a rational interval arithmetic where real number calculations take place in an algebraic setting. In order to reduce the dependency effect of interval arithmetic, we integrate two techniques: interval splitting and Taylor series expansions. This pragmatic approach has been developed, and formally verified, in a theorem prover. The formal development also includes a set of customizable strategies to automate proofs involving explicit calculations over real numbers. Our ultimate goal is to provide guaranteed proofs of numerical properties with minimal human theorem-prover interaction.
Real number calculations, interval arithmetic, proof checking, theorem proving.

C. Muñoz, M. Daumas and D. Lester, "Verified Real Number Calculations: A Library for Interval Arithmetic," in IEEE Transactions on Computers, vol. 58, no. , pp. 226-237, 2008.
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