§2-1 Plane Stress Problem and Plane Strain Problem §2-2 Equilibrium Differential Equation §2-3 The Stress State at a Point in a Plane Problem §2-4 Geometrical Equation. The Displacement of the Rigid Body §2-5 Physical Equation §2-6 Boundary Conditions §2-7 Saint-Venant’s Principle and Its Application §2-8 Solving the Plane Problem According to the Displacement §2-9 Solving the Plane Problem According to the Stress. Compatibility Equations §2-10 The Simplification under the Constant Body Force. Stress Function