$$\sigma = \fracFA = \frac5 , \textkN78.5 , \textmm^2 = 63.7 , \textMPa$$
The state of plane stress at a point on the surface of a machine component is represented by the element shown in Fig. P2.xx. Determine: (a) The principal stresses and the orientation of the principal planes. (b) The maximum in-plane shear stress and the associated average normal stress. (c) Sketch the stress element oriented at the principal angle. $$\sigma = \fracFA = \frac5 , \textkN78