(Solved): Evaluate the following integral using trigonometric substitution. \[ \int \frac{d x}{\sqrt{x^{2}-81 ...

Evaluate the following integral using trigonometric substitution. \[ \int \frac{d x}{\sqrt{x^{2}-81}}, x>9 \] What substitution will be the most helpful for evaluating this integral? A. \( x=9 \sec \theta \) B. \( x=9 \sin \theta \) C. \( x=9 \tan \theta \) Rewrite the given integral using this substitution. \[ \int \frac{d x}{\sqrt{x^{2}-81}}=\int(1 d \theta \] (Simplify your answers. Type exact answers.)