86.9 Chapter 7. Polar coordinates and vectors. Exercise 7a at page 109

86.9.1 problem 9
86.9.2 problem 10
86.9.3 problem 11
86.9.4 problem 12
86.9.5 problem 13
86.9.6 problem 14
86.9.7 problem 15
86.9.8 problem 16
86.9.9 problem 17
86.9.10 problem 18