Make the Indicated Trigonometric Substitution in the Given Algebraic Expression $0 \leq x \leq \pi / 2$

Essay

Make the indicated trigonometric substitution in the given algebraic expression and simplify. Assume that $0 \leq x \leq \pi / 2$ $\sqrt { 16 - x ^ { 2 } } , \quad x = 4 \sin \theta$