고체역학 (Gere) — Analysis of Stress and Strain: Problem 7.3-4

7.3-4 An element in plane stress is subjected to stresses \(\sigma_x = 105 \text{ MPa}\), \(\sigma_y = 75 \text{ MPa}\), and \(\tau_{xy} = 25 \text{ MPa}\) (see the figure for Problem 7.3-1). Determine the principal stresses and show them on a sketch of a properly oriented element.