Figure 5 shows Mohr–Coulomb yield surface in the three-dimensional space of principal stresses. It is a conical prism and formula_99 determines the inclination angle of conical surface. Figure 6 shows Mohr–Coulomb yield surface in two-dimensional stress space. In Figure 6 formula_100 and formula_101 is used for formula_97 and formula_96, respectively, in the formula. It is a cross section of this conical prism on the plane of formula_49. In Figure 6 Rr and Rc are used for Syc and Syt, respectively, in the formula.