Use the Trigonometric Substitution to Rewrite the Algebraic Expression as a Trigonometric

Multiple Choice

Use the trigonometric substitution to rewrite the algebraic expression as a trigonometric function of θ,where $0 < \theta < \frac { \pi } { 2 }$ . $\sqrt { 36 - 9 x ^ { 2 } } , x = 2 \cos \theta$ ​

A) 2 cos θ
B) 36 sin θ
C) - 2 sin θ
D) 36 cos θ
E) 6 sin θ