Find an Algebraic Expression Equivalent to the Given Expression $\cos ( \operatorname { arccot } u )$

Multiple Choice

Find an algebraic expression equivalent to the given expression.
- $\cos ( \operatorname { arccot } u )$

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