tečné vektory \[P^u(u,v)= \frac{\partial P(u,v)}{\partial u}=\bigg(\frac{\partial x(u,v)}{\partial u},\frac{\partial y(u,v)}{\partial u},\frac{\partial z(u,v)}{\partial u}\bigg)\] \[P^v(u,v)= \frac{\partial P(u,v)}{\partial v}=\bigg(\frac{\partial x(u,v)}{\partial v},\frac{\partial y(u,v)}{\partial v},\frac{\partial z(u,v)}{\partial v}\bigg)\]
tečná rovina a normála
\[\vec{n}(u,v)=P^u(u,v)\times P^v(u,v)\]
vektor zkrutu \[P^{uv}(u,v)=\frac{\partial^2 P(u,v)}{\partial u\partial v}=\frac{\partial^2 P(u,v)}{\partial v\partial u}\]