고체역학 (Gere) — Analysis of Stress and Strain: Problem 7.3-1

7.3-1 The stresses acting on an element are \(\sigma_x = 3 \text{ MPa}\), \(\sigma_y = 5 \text{ MPa}\), and \(\tau_{xy} = 2.8 \text{ MPa}\). Determine the principal stresses and show them on a sketch of a properly oriented element.