A "perfect" square (shown in dashed lines in the sketch below) with initial dimensions of 0.5 x 0.5 inch is drawn on the surface of a thin aluminum structure (E = 10x10^{6} psi, v = 0.33). The structure is then loaded and the square deforms as shown:
(a) Determine the principal stresses induced in the structure:
(b) Determine the angle between the +x-axis and the +1 axis