  In this work we provide an algorithm approximating the tangent bivector at a
point of a smooth surface through inscribed triangles converging to the point,
regardless their form or position with respect to the tangent plane. This
result is obtained approximating Jacobian determinants of smooth plane
transformations at a point x through nondegenerate triangles converging to x.
We can also approximate the area of a portion of a smooth surface, through a
slightly modified notion of area of inscribed triangular polyhedra approaching
the surface (without any kind of constraint due to the Schwarz paradox).
