Evaluate the Integral Using the Indicated Trigonometric Substitution $\int \frac{d x}{x^{2} \sqrt{x^{2}-36}} ; x=6 \sec \theta$

Evaluate the integral using the indicated trigonometric substitution. $\int \frac{d x}{x^{2} \sqrt{x^{2}-36}} ; x=6 \sec \theta$