
 lecture 6 (Site not responding. Last check: 20071012) 
  Geometric interpretation of partial derivatives: The partial derivative of a function f(x,y) with respect to x can be interpreted as the slope of the curve obtained by cutting the graph of f(x,y) (i.e., the surface z=f(x,y)) at a fixed yvalue; a similar interpretation holds for the partial derivative with respect to y. 
  Computation of partial derivatives: If, as is usually the case, f(x,y) is given by a formula, the computation of the partial derivatives of f boils down to ordinary differentiation. 
  Partial differential equations (PDE's): A PDE is an equation for a function of several variables involving partial derivatives of that function. 
 www.math.uiuc.edu /~dikim/m242/lec6.html (752 words) 
