In the space , the vector
directed from the origin to a point \,\, is the position vector of this point.\, When the point is variable, represents a vector field and its length
a scalar field.
The simple formulae
are valid, where is the unit vector having the direction of .
If\, Failed to parse (syntax error): {\displaystyle \vec}
\, is a constant vector,\, \, a vector function and\, \, is a twice differentiable function, then the formulae
- Failed to parse (syntax error): {\displaystyle \nabla(\vec\cdot\!\vec{r}) = \vec}
hold.
- ↑ {\sc K. V\"ais\"al\"a:} Vektorianalyysi . \,Werner S\"oderstr\"om Osakeyhti\"o, Helsinki (1961).