6. We will evaluate 2 - 9 dr in the following steps. (a) Using an appropriate trigonometric substitution, transform the above integral into sin2 0 de. (b) Integrate sin2 0 do using the Half-Angle formula. (c) Using the results in parts (a) and (b), plus the Double-Angle formula, show that /2 - 9 de = Vx2 - 9 - sec 23 + C. 2x2