Write the Trigonometric Expression as an Algebraic Expression in U $\cos \left( \tan ^ { - 1 } \mathrm { u } \right)$

Multiple Choice

Write the trigonometric expression as an algebraic expression in u.
- $\cos \left( \tan ^ { - 1 } \mathrm { u } \right)$

A) $\mathrm { u } \sqrt { \mathrm { u } ^ { 2 } + 1 }$
B) $\frac { \mathrm { u } } { \sqrt { \mathrm { u } ^ { 2 } + 1 } }$
C) $\frac { 1 } { \sqrt { \mathrm { u } ^ { 2 } + 1 } }$
D) $\frac { 1 } { \sqrt { u ^ { 2 } - 1 } }$