At a point in a stressed body, the stresses are $\sigma_x = 1.0 MPa$, $\sigma_y = 3.0 MPa$, $\sigma_z = 5.0 MPa$, $\tau_{xy} = 4.0 MPa$, $\tau_{zx} = 6.0 MPa$, and $\tau_{yz} = 8.0 MPa$. Determine:
a)the resultant stress S,
b)normal stress $\sigma_n$ and shear stress $\tau_{n}$, on a plane whose outward normal makes equal angles with the x, y, z axes $[l=m=n]$,
c)stress invariants and principal stresses,
d)absolute maximum shear stress.