Tangent Planes (Real Parametric Surfaces)#
Definition: Tangent Plane
Let \(\phi: \mathcal{D} \subseteq \mathbb{R}^2 \to \mathbb{R}^n\) be a parametric surface which is regular at an interior point \(\boldsymbol{p}\) of \(\mathcal{D}\).
The tangent plane of \(\phi\) at \(\boldsymbol{p}\) is the span of its partial derivatives there:
\[\operatorname{span}\{\partial_1 \phi(\boldsymbol{p}), \partial_2 \phi(\boldsymbol{p}) \}\]