A particle in three-dimensional space moves along the path: $\vec { r } ( t ) = \left\langle t ^ { 2 } , \sin ( t ) , e ^ { t } \right\rangle$. Find the time when the particle changes direction.
A particle in three-dimensional space moves along the path:\\
$\vec { r } ( t ) = \left\langle t ^ { 2 } , \sin ( t ) , e ^ { t } \right\rangle$.\\
Find the time when the particle changes direction.