Find the Unit Tangent Vector of the Given Curve $$r ( t ) = \left( 5 \sin ^ { 3 } 9 t \right) i + \left( 5 \cos ^ { 3 } 9 t \right) \mathbf { j }$$

Multiple Choice

Find the unit tangent vector of the given curve.
- $$r ( t ) = \left( 5 \sin ^ { 3 } 9 t \right) i + \left( 5 \cos ^ { 3 } 9 t \right) \mathbf { j }$$

A) T = (5 sin 9t) i - (5 cos 9t) j
B) T = (sin 9t) i - (cos 9t) j
C) T = (135 sin 9t) i -(135 cos 9t) j
D) T = (5 cos 9t) i - (5 sin 9t) j