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A new proof for the Euler theorem in the complex numbers theory
(2010-05-17)
In the paper, a new proof for the Euler equation (exp(ix) = cos x + i sin x) has been
presented. At first, a new and general formula has been proved from which the Euler equation
has been derived.
Almost preenvelopes of commutative rings
(2010-05-16)
We study almost F-preenvelopes in the category of rings, for a significative class F of commutative rings. We completely identify those rings which have an almost F-preenvelope when F is the class of fields, semisimple ...
Teoremas del punto fijo para T−operadores de Banach
(2010-05-16)
En este artículo estudiamos la existencia de puntos fijos para T−operadores de Banach
Minimal R1, minimal regular and minimal presober topologies
(2010-03-18)
By means of filters, minimal R1 and minimal regular topologies are characterized on suitable intervals consisting of non-trivial R0 topologies.
Envelopes of commutative rings
(2010-03-18)
Given a significative class F of commutative rings, we study the precise conditions under which a commutative ring R has an F-envelope. A full answer is obtained when F is the class of fields, semisimple commutative rings ...
A lower bound for the spectral radius of a digraph
(2010-03-18)