Assignment:
Consider the function f(x,y,z) = (e^z)ln(x^2 + y^2)
a) Is there a vector r such that the directional derivative of f at (1,1,0) in the direction of r equals 1? If there is, find one such vector. If not, explain why not.
b) Is there a vector r such the directional derivative of f at (1,1,0) in the direction of r equals to -2? If there is, find one such vector. If not, explain why not.
Provide complete and step by step solution for the question and show calculations and use formulas.