Let $z = \ln \sqrt { x ^ { 2 } + y ^ { 2 } }$

Essay

Let $z = \ln \sqrt { x ^ { 2 } + y ^ { 2 } }$ , $x = r \cos \theta$ , and $y = r \sin \theta$ . Use the chain rule to find $\frac { \delta z } { \delta r }$ and $\frac { d z } { \delta \theta }$ .