**Math 3592H Honors Mathematics I Fall Semester 2003
**

Exercises:

Section 1.6 (pages 124-125): 4*

Extra Questions

1. For each of the following functions find the directional derivative in the direction of the unit vector

2. Show that the function f defined by

has a directional derivative in every direction at (0,0), but that f is not differentiable at (0,0).

[Hint: If f were differentiable at (0,0) then we would have f'(0,0)=0.]