Gráfico
$\small G_f=\{\, (x,y,z) \in \mathbb{R}^3 : \, (x,y) \in D_f \, \wedge \, z=f(x,y) \,\}$
$\small G_f=\{\, (x,y,z) \in \mathbb{R}^3 : \, (x,y) \in D_f \, \wedge \, z=f(x,y) \,\}$
$\small c_k=\{\, (x,y) \in D_f : \, f(x,y)=k \,\}$
$\small f_x(x,y)\,,\,f_y(x,y)$
$\small \vec{v}=(f_x(x_0,y_0),f_y(x_0,y_0),-1)$
$\small \nabla f(x,y)$
$\small f_\vec{u}(x,y)$
$\small \nabla f(x,y)=\vec{0}$
$\small C=\text{int} \, C \cup \text{front} \, C$
$\small \nabla f(x,y)=\lambda\nabla g(x,y)$
$\small \int\!\!\int_{R} f(x,y) \, dA$