87.27 Chapter 6. Boundary value problems. Exercise at page 262

87.27.1 problem 1
87.27.2 problem 2
87.27.3 problem 6
87.27.4 problem 7
87.27.5 problem 8
87.27.6 problem 10
87.27.7 problem 11
87.27.8 problem 11
87.27.9 problem 15
87.27.10 problem 17
87.27.11 problem 18