Let $x ( t ) = e ^ { t } \sin t , y ( t ) = e ^ { t } \cos t$

Multiple Choice

Let $x ( t ) = e ^ { t } \sin t , y ( t ) = e ^ { t } \cos t$ be the parametric equations of a curve. Then $\frac { d y } { d x }$ is

A) $- \frac { \cos t - \sin t } { \cos t + \sin t }$
B) $\frac { \cos t + \sin t } { \cos t - \sin t }$
C) $- \frac { \cos t + \sin t } { \cos t - \sin t }$
D) $\frac { \cos t - \sin t } { \cos t + \sin t }$
E) $\frac { \cos t - \sin t } { 2 ( \cos t + \sin t ) }$