고체역학 (Gere) — Analysis of Stress and Strain: Problem 7.2-23

7.2-23 A gusset plate on a truss bridge is in plane stress with normal stresses \(\sigma_x\) and \(\sigma_y\) and shear stress \(\tau_{xy}\), as shown in the figure. At counterclockwise angles \(\theta = 32^\circ\) and \(\theta = 78^\circ\) from the \(x\) axis, the normal stress is 29 MPa in tension. If the stress \(\sigma_x\) equals 18 MPa in tension, what are the stresses \(\sigma_y\) and \(\tau_{xy}\)?