Extracted text: For a square cross-section bar affected by torsional moment at both ends, the stress components are shown as follows (opposite the figure): a) Find the principal directions for the zero principal stress? b) For the following special case, show that the stress vector on the lateral surface of the rod is zero: 4 = (xỉ – a?xx? - a²) %3D c) Also the torsional moment at each of the two ends of the rod is equal to: M = 32 4 = f(x1, X2) ax2 011 = 022= 033 = 012 = 0 X2 221 PM Links 69% 44°F Rain and snow ENG 1/16/2022