Use the Trigonometric Substitution U = a Csc $\theta$ , Where 0

Multiple Choice

Use the trigonometric substitution u = a csc $\theta$ , where 0 < $\theta$ < $\pi$ /2 and a > 0 to simplify the expression $\sqrt { u ^ { 2 } - a ^ { 2 } }$ .

A) a tan $\theta$
B) - a cot $\theta$
C) a csc $\theta$
D) a cos $\theta$
E) a cot $\theta$