vpotential takes two arguments : a vector field
V
in R^{n} with respect to n real variables
and the vector of these variable names.

vpotential returns, if it is possible, a vector U such
that curl(U)=V.
When it is possible we say that V is a conservative flux
field or a solenoidal field.
The general solution is the sum of a particular solution and of the
gradient of an arbitrary function, Xcas returns a particular
solution with zero as first component.

vpotential is the reciprocal function of curl.

Input :

vpotential([2*x*y+3,x

`^`

2-4*z,-2*y*z],[x,y,z]) Output :

[0,(-(2*y))*z*x,-x

`^`

3/3-(-(4*z))*x+3*y]
In ℝ^{3}, a vector field V is a rotational
if and only if its
divergence is zero

(divergence(V,[x,y,z])=0).
In time-independent electro-magnetism,
V= B is the magnetic field and
U= A is the potential vector.