Evaluate the Quantity Without Using a Calculator or Tables $\cos \left( \arctan \frac { 1 } { \sqrt { 3 } } \right)$

Multiple Choice

Evaluate the quantity without using a calculator or tables. $\cos \left( \arctan \frac { 1 } { \sqrt { 3 } } \right)$

A) 1/2
B) $\frac { \sqrt { 3 } } { 2 }$
C) $- \frac { \sqrt { 3 } } { 2 }$
D) -1/2
E) $\frac { \sqrt { 3 } } { 3 }$