Potential : potential

### 2.50.6 Potential : `potential`

`potential` takes two arguments : a vector field V in Rn with respect to n real variables and the vector of these variable names.
`potential` returns, if it is possible, a function U such that grad(U)=V. When it is possible we say that V derive of the potential U, and U is defined up to a constant.
`potential` is the reciprocal function of `derive`.
Input :

`potential([2*x*y+3,x```^```2-4*z,-4*y],[x,y,z])`

Output :

`2*y*x```^```2/ 2+3*x+(x```^```2-4*z-2*x```^```2/2)*y`

Note that in ℝ3 a vector V is a gradient if and only if it’s rotationnal is zero i.e. if `curl(V)=0`. In time-independant electro-magnetism, V=E is the electric field and U is the electric potential.