Del (ナブラ演算子)

curl gradf=0div curlA=0curlcurlA=∇(∇⋅A)−∇2A\begin{aligned} \mathrm curl \ \mathrm grad f & = & \mathbf{0} \\ \mathrm div \ \mathrm curl \mathbf{A} & = & \mathbf{0} \\ \mathrm curl \mathrm curl \mathbf{A} & = & \nabla (\nabla \cdot \mathbf{A}) - \nabla^2 \mathbf{A} \end{aligned}