The stresses at a point in plane stress on a sheet metal roof were found to be sigma_xx = 10 ksi (C), sigma_yy = 20 ksi (C) and Tau_xy = 30 ksi using matrix methods a) determine the normal and shear stresses on a plane passing through the point that is 42 degrees counter-clockwise from the x-axis b) determine the principal stresses and principal direction one c) determine the maximum shear stress at the point.