La derivada en varias variables como analog\'ia formal de su hom\'onima   escalar
  Some formal analogies between the Differential Calculus in One Variable and the Differential Calculus in Several Variables are presented. It is studied and introduced the derivability of functions at several variables from the single variable conceptual analogous. This is obtained from exploring the dynamic image of limit of a family of slopes of secants planes to the graphic of a bivariate function. 
M. Bravo-Gaete, F. C\'ordova-Lepe, P.Dotte
math.HO