Revision history [back]

In section 14.5, question #6, it asks: Suppose the electric potential at $(x,y)$ is $ln\sqrt (x^2+y^2)$. Find the rate of change of the potential at $(3,4)$ toward the origin and also in a direction at a right angle to the direction toward the origin.

I know how to calculate $D_uf$ but I am lost on what $u$ would be in this problem.

In section 14.5, question #6, it asks: Suppose the electric potential at $(x,y)$ is $ln\sqrt (x^2+y^2)$. {(x^2+y^2)}$. Find the rate of change of the potential at $(3,4)$ toward the origin and also in a direction at a right angle to the direction toward the origin.

I know how to calculate $D_uf$ but I am lost on what $u$ would be in this problem.