Find the Unit Tangent Vector of the Given Curve $\mathbf { T } = ( 7 \cos t ) \mathbf { j } - ( 7 \sin t ) \mathbf { k }$

Multiple Choice

Find the unit tangent vector of the given curve.
-r(t) = (7t cos t - 7 sin t) j + (7t sin t + 7 cos t) k

A) $\mathbf { T } = ( 7 \cos t ) \mathbf { j } - ( 7 \sin t ) \mathbf { k }$
B) $\mathbf { T } = ( - 7 \sin t ) \mathbf { j } + ( 7 \cos t ) \mathbf { k }$
C) $\mathbf { T } = ( - \sin t ) \mathbf { j } + ( \cos t ) \mathbf { k }$
D) $\mathbf { T } = - \frac { 1 } { 7 } ( \sin t ) \mathbf { j } + \frac { 1 } { 7 } ( \cos t ) \mathbf { k }$