Use the Chain Rule to Find $\frac { \partial z } { \partial s }$

Multiple Choice

Use the Chain Rule to find $\frac { \partial z } { \partial s }$ . $z = e ^ { y } \cos ( \theta ) , r = 8 s t , \theta = \sqrt { s ^ { 2 } + t ^ { 2 } }$

A) $\frac { \partial z } { \partial s } = e ^ { \gamma } \left( 8 t \cos ( \theta ) - \frac { s \sin ( \theta ) } { \sqrt { s ^ { 2 } + t ^ { 2 } } } \right)$
B) $\frac { \partial z } { \partial s } = e ^ { \gamma } \left( 8 t \cos ( \theta ) + \frac { s \sin ( \theta ) } { \sqrt { s ^ { 2 } - t ^ { 2 } } } \right)$
C) $\frac { \partial z } { \partial s } = \left( 8 t \cos ( \theta ) + \frac { s e ^ { \gamma } \sin ( \theta ) } { \sqrt { s ^ { 2 } + t ^ { 2 } } } \right)$
D) $\frac { \partial z } { \partial s } = e ^ { \gamma } \left( \cos ( \theta ) + \frac { s \sin ( \theta ) } { \sqrt { s ^ { 2 } - t ^ { 2 } } } \right)$
E) $\frac { \partial z } { \partial s } = e ^ { \gamma } \left( t \cos ( \theta ) - \frac { s \sin ( \theta ) } { \sqrt { s ^ { 2 } + t } } \right)$