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(* Micromega: A reflexive tactic using the Positivstellensatz           *)
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(*  Frédéric Besson (Irisa/Inria) 2006-2008                             *)
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Open Scope R_scope.
(* Other (simple) examples *)
Goal forall x, -x^2 >= 0 -> x - 1 >= 0 -> False.
Goal forall x, -x^2 >= 0 -> x - 1 >= 0 -> False.

Lemma l1 : forall x y z : R, Rabs (x - z) <= Rabs (x - y) + Rabs (y - z).