Plot two points C and E of coordinates (67.2, 84.64) and (-61.35, 68.57), respectively as in Fig. 2.16. Join C and E. Draw perpendicular bisector AB of CE intersecting normal stress axis at point G. With point G as center, draw Mohr’s circle passing through C and E. Point A on diameter AB at an angle 2\theta = -40°, clockwise to point E gives stresses on plane R.