8. Evaluate x (x + 4)3 da in the following steps. (a) Set up a Trigonometric Substitution with an appropriate right triangle and relation between x and the reference angle 0. Transform the above integral into sino tan do. (b) Using cos + sin = 1, verify the following trigonometric identity: sintan = sec + cos (c) Using the results in parts (a) and (b), plus the given formula sheet, evaluate I dx. (x+4)3