(a) Equations 6.4a and 6.4b are expressions for

(a) Equations 6.4a and 6.4b are expressions for normal (s’) and shear (t’) stresses, respectively, as a function of the applied tensile stress (s) and the inclination angle of the plane on which these stresses are taken (? of Figure 6.4). Make a plot on which is presented the orientation parameters of these expressions (i.e., cos2 ? and sin ? cos ?) versus ?.
(b) From this plot, at what angle of inclination is the normal stress a maximum?
(c) Also, at what inclination angle is the shear stress a maximum?