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# Copyright (C) 2006-2007 Anders Logg (logg@simula.no) and Marie Rognes (meg@math.uio.no)"
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# Licensed under the GNU LGPL Version 2.1
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# The bilinear form a(v, u) and linear form L(v) for
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# a mixed formulation of Poisson's equation with BDM
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# (Brezzi-Douglas-Marini) elements.
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# Compile this form with FFC: ffc -l dolfin MixedPoisson.form
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BDM = FiniteElement("Brezzi-Douglas-Marini", "triangle", q)
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DG = FiniteElement("Discontinuous Lagrange", "triangle", q - 1)
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mixed_element = BDM + DG
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(tau, w) = TestFunctions(mixed_element)
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(sigma, u) = TrialFunctions(mixed_element)
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a = (dot(tau, sigma) - div(tau)*u + w*div(sigma))*dx