ABSTRACT
This chapter discusses the differentiability of functions of several variables. It introduces first the partial derivatives, the equation of the tangent plane and the normal line to a surface in. The chapter then focuses on the differentiability which is further extended to vector valued functions. Geometrically, the derivative of a single variable function is the slope of the tangent line to its graph. The chapter discusses the geometric interpretation of the partial derivatives of a function. The plane that contains the tangent lines T1 and T2 is called the tangent plane to the surface S at the point P. The line which is orthogonal to the tangent plane at P is called the normal line to the surface S. The chapter also discusses differentiability of Vector-Valued Functions.
