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COMSOL Multiphysics™

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femdiff<br />

Purpose<br />

femdiff<br />

Symbolically differentiate a PDE in general form.<br />

Syntax<br />

Description<br />

fem1 = femdiff(fem,...)<br />

xfem1 = femdiff(xfem,...)<br />

fem1 = femdiff(fem,...) symbolically differentiates the Γ, F, G, and R<br />

coefficients in a PDE given in general form. xfem can also be an extended FEM<br />

structure. In this case, femdiff differentiates all FEM structures in general form.<br />

The coefficients are obtained from the ga, f, and g, r fields from the fem.equ and<br />

fem.bnd structures, respectively. It returns a FEM structure where the fields equ<br />

and bnd have been updated with the fields c, al, be, a, and q, h according to“The<br />

Linear or Linearized Model” on page 378 in the <strong>COMSOL</strong> Multiphysics User’s<br />

Guide.<br />

The expressions in the coefficients Γ, F, G, and R can contain expressions<br />

containing the binary operators +, -, *, /, ^, ==, ~=, >, >=,

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