In Fig. 2.12, diameter OA represents the state of stress in x — y plane. Draw a circle through OA. Perpendicular diameter BC represents plane of maximum shear stress. Draw DC at 2\theta = 120° to OA. Point D represents the stress on the plane inclined at 60° to the vertical plane.

Resultant stress, \sigma _r = OD = 35  MPa

Inclination of \theta _r  \text{w.r.t. its normal} = \angle  DOC = 60°