12 Chapter 1, section 1.2. Riccati Equation. subsection 1.2.6-4. Equations with cotangent.

12.1 problem 38
12.2 problem 39
12.3 problem 40
12.4 problem 41
12.5 problem 42
12.6 problem 43
12.7 problem 44
12.8 problem 45
12.9 problem 46