Exercise 7.2/21 - Use the Suggestion box on page 498

Exercise 7.2/22 - Use the Suggestion box on page 498

Exercise 7.2/33 - Use the fact that (sec(x))' = tan(x) sec(x), then integrate by parts, 
                  and use (without deriving it) the formula for integral of sec(x) on page 499 

Exercise 7.2/46 - Use the formulas from part (c) of the Suggestion box on page 497