linalg[grad] - vector gradient of an expression
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Calling Sequence
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grad(expr, v)
grad(expr, v, co)
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Parameters
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expr
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scalar expression
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v
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vector or list of variables
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co
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(optional), is either of type `=` or a list of three elements. This option is used to compute the gradient in orthogonally curvilinear coordinate systems.
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Description
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The function grad computes the gradient of expr with respect to v.
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It computes the following vector of partial derivatives:
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vector( [diff(expr, v[1]), diff(expr, v[2]), ...] ).
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In the case of three dimensions, where expr is a scalar expression of three variables and v is a list or a vector of three variables:
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If the optional third argument co is of the form coords = coords_name or coords = coords_name({[const]}), grad will operate on commonly used orthogonally curvilinear coordinate systems. See ?coords for the list of the different coordinate systems known to Maple.
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For orthogonally curvilinear coordinates v[1], v[2], v[3]
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with unit vectors a[1], a[2], a[3], and scale factors
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h[1], h[2], h[3]:
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Let the rectangular coordinates x, y, z be defined in terms of the
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specified orthogonally curvilinear coordinates. We have:
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h[n]^2 = [diff(x,v[n])^2 + diff(y,v[n])^2 + diff(z,v[n])^2], n=1,2,3.
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The formula for the gradient vector is:
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grad(expr) = sum(a[n]/h[n]*diff(expr,v[n]),n=1..3);
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If the optional third argument co is a list of three elements which specify the scale factors, grad will operate on orthogonally curvilinear coordinate systems.
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To compute the gradient in other orthogonally curvilinear coordinate systems, use the addcoords routine.
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The two dimensional case is similar to the three dimensional one.
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The command with(linalg,grad) allows the use of the abbreviated form of this command.
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Examples
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Important: The linalg package has been deprecated. Use the superseding packages, LinearAlgebra and VectorCalculus, instead.
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define the scale factors in spherical coordinates
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