The Radius of Curvature Of $\mathbf { r } ( t ) = \cos ( 2 t ) \mathbf { i } + \sin ( 2 t ) \mathbf { j } + t \mathbf { k }$

Multiple Choice

The radius of curvature of $\mathbf { r } ( t ) = \cos ( 2 t ) \mathbf { i } + \sin ( 2 t ) \mathbf { j } + t \mathbf { k }$ at the point corresponding to t = 0 is

A) $4 \sqrt { 2 }$
B) $\frac { 1 } { 2 \sqrt { 2 } }$
C) 2
D) $\frac { 3 } { \sqrt { 2 } }$
E) 5
4