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(*  Title:      HOL/Integ/IntRing.ML
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    ID:         $Id$
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    Author:     Tobias Nipkow and Markus Wenzel
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    Copyright   1996 TU Muenchen
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The instantiation of Lagrange's lemma for int.
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*)
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Goal "!!i1::int. \
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\  (sq i1 + sq i2 + sq i3 + sq i4) * (sq j1 + sq j2 + sq j3 + sq j4) = \
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\  sq(i1*j1 - i2*j2 - i3*j3 - i4*j4)  + \
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\  sq(i1*j2 + i2*j1 + i3*j4 - i4*j3)  + \
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\  sq(i1*j3 - i2*j4 + i3*j1 + i4*j2)  + \
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\  sq(i1*j4 + i2*j3 - i3*j2 + i4*j1)";
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by (rtac Lagrange_lemma 1);
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qed "Lagrange_lemma_int";
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